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Verification and validation

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"IV&V" redirects here. For NASA's IV&V Facility, see Independent Verification and Validation Facility.

Verification and validation is the process of checking that a product, service, or system meets specifications and that it fulfills its intended purpose. These are critical components of a quality management system such as ISO 9000. Sometimes preceded with "Independent" (or IV&V) to ensure the validation is performed by a disinterested third party.

Overview

Verification is a Quality control process that is used to evaluate whether or not a product, service, or system complies with regulations, specifications, or conditions imposed at the start of a development phase. Verification can be in development, scale-up, or production. This is often an internal process.

Validation is Quality assurance process of establishing evidence that provides a high degree of assurance that a product, service, or system accomplishes its intended requirements. This often involves acceptance of fitness for purpose with end users and other product stakeholders.

It is sometimes said that validation can be expressed by the query "Are you building the right thing?" and verification by "Are you building it right?" "Building the right thing" refers back to the user's needs, while "building it right" checks that the specifications be correctly implemented by the system. In some contexts, it is required to have written requirements for both as well as formal procedures or protocols for determining compliance.

Activities

Verification of machinery and equipment usually consists of Design Qualification - DQ [1], Installation Qualification - IQ [2], Operational Qualification - OQ [3] and Performance Qualification - PQ [4]. DQ is usually a vendor's job. However, DQ can also be performed by the user, by confirming through review and testing that the equipment meets the written acquisition specification. If the relevant document or manuals of machinery/equipment are provided by vendors, the later 3Q needs to be thoroughly performed by the users who work in an industrial regulatory environment. Otherwise, the process of IQ, OQ and PQ is the task of validation. The typical example of such a case could be the loss or absence of vendor's documentation for legacy equipment or do-it-yourself (DIY) assemblies (i.e., cars, computers etc.) and, therefore, users should endeavour to acquire DQ document beforehand. Each template of DQ, IQ, OQ and PQ usually can be found on the internet respectively, whereas the DIY qualifications of machinery/equipment can be assisted either by the vendor's training course materials and tutorials, or by the published guidance books, such as step-by-step series if the acquisition of machinery/equipment is not bundled with on- site qualification services. This kind of the DIY approach is also applicable to the qualifications of software, computer operating systems and a manufacturing process. The most important and critical task as the last step of the activity is to generating and archiving machinery/equipment qualification reports for auditing purposes, if regulatory compliances are mandatory. At the same time, one should bear in mind to kindly share the original work with others, if the activity, especially validation of newly invented machinery/equipment, is worth of publishing.

Qualification of machinery/equipment is venue dependent and re-qualification needs to be conducted once the objects are relocated. The full scales of some equipment qualifications are even time dependent, and hence re-certification is necessary when a specified due time laps [5], [6]. Re-qualification of machinery/equipment should also be conducted when replacement of parts, or coupling with another device, or installing a new application software and restructuring of the computer which affects especially the pre-settings, such as on BIOS, registry, disk drive partition table, or an ini file etc, have been necessary. In such a situation, the specifications of the parts/devices/software and restructuring proposals should be appended to the qualification document whether the parts/devices/software are genuine or not. Torres and Hyman have discussed the suitability of non genuine parts for clinical use and provided guidelines for equipment users to select appropriate substitutes which are capable to avoid adverse effects [7]. In the case when genuine parts/devices/software are demanded by some of regulatory requirements, then re-qualification does not need to be conducted on the non genuine assemblies. Instead, the asset has to be recycled for non regulatory purposes.

When machinery/equipment qualification is conducted by a standard endorsed third party such as by an ISO standard accredited company for a particular division, the process is called certification [8], [9]. Currently, the coverage of ISO/IEC 15408 certification by an ISO/IEC 27001 accredited organization is limited, the scheme requires a fair amount of efforts to get popularized.

Categories of verification & validation

Validation work can generally be categorized by the following functions:

  • Prospective validation - the missions conducted before new items are released to make sure the characteristics of the interests which are functional properly and which meet the safety standards [10], [11]. Some examples could be legislative rules, guidelines or proposals [12], [13], [14], methods [15], theories/hypothesis/models [16], [17], products and services [18], [19]
  • Retrospective validation - a process for items that are already in use and distribution or production. The validation is performed against the written specifications or predetermined expectations, based upon their historical data/evidences that are documented/recorded. If any critical data is missing, then the work can not be processed or can only be completed partially [10], [20], [21]. The tasks are considered necessary [22] if
    • prospective validation is missing, inadequate or flawed.
    • the change of legislative regulations or standards affects the compliance of the items being released to the public or market.
    • reviving of out-of-use items
Some of the examples could be validating of
  • ancient scriptures that remain controversies [23], [24]
  • clinical decision rules [25]
  • data systems [26], [27]
  • Full scale validation
  • Partial validation - often used for research and pilot studies if time is constrained. The most important and significant effects are tested. From an analytical chemistry perspective, those effects are selectivity, accuracy, repeatability, linearity and its range.
  • Cross-validation
  • Re-validation/Locational or Periodical validation - carried out, for the item of interest that is dismissed, repaired, integrated/coupled, relocated, or after a specified time laps. Examples of this category could be relicencing/renewing driver's license, recertifying an analytical balance that has been expired or relocated, and even revalidating professionals [28], [29]. Re-validation may also be conducted when/where a change occurs during the courses of activities, such as scientific researches or phases of clinical trial transitions. Examples of these changes could be
In GLP accredited laboratories, verification/revalidation will even be conducted very often against the monographes of USP and BP to cater for domestic needs [38].
  • Concurrent validation - conducted during a routine processing of services, manufacturing or engineering etc. Examples of these could be

Aspects of validation

The most tested attributes in validation tasks may include, but are not limited to

  • Selectivity/specificity
  • Accuracy
  • Precision/Repeatability
  • Reproducibility
  • Limit of detection - especially for trace elements
  • Limit of quantification
  • Curve fitting and its range
  • System suitability - In a broad way, it usually includes a test of ruggedness among inter-colaborators, or a test of robustness within an organization [39], [40], [41]. However, the U.S. Food and Drug Administration (FDA) has specifically defined it for its administration, as "System suitability testing is an integral part of many analytical procedures. The tests are based on the concept that the equipment, electronics, analytical operations and samples to be analyzed constitute an integral system that can be evaluated as such. System suitability test parameters to be established for a particular procedure depend on the type of procedure being validated." [42]. In some cases of analytical chemistry, a system suitability test could be rather a method specific than universal. Such examples are chromatographic analysis, which is usually media (column, paper or mobile solvent) sensitive [43], [44], [45]. However to the date of this writing, this kind of approaches are limited to some of pharmaceutical compendial methods, by which the detecting of impurities, or the quality of the intest analyzed are critical (i.e., live and death). This is probably largely due to
  • their intensive labouring demands and time consumption [46] [clarification needed]
  • their confinements by the definition of the term defined by different standards.
To solve this kind of difficulties, some regulatory bodies or compendial methods usually provide the advices on what the circumstances or conditions that the performing of a specified system suitability test should be beared and compulsory.

Industry references

These terms generally apply broadly across industries and institutions. In addition, they may have very specific meanings and requirements for specific products, regulations, and industries. Some examples:

  • Software and computer systems
    Main article: Verification and Validation (software)
  • Food and Drug
    • Pharmaceuticals The design, production, and distribution of drugs are highly regulated. This includes software systems. For example in the USA, the Food and Drug Administration have regulations in Part 21 of the Code of Federal Regulations [1]. Nash et al. have published a book which provides a comprehensive coverage on the various validation topics of pharmaceutical manufacturing processes [47]. Some companies are taking a risk-based approach to validating their GAMP system if one understands the regulatory requirements very well while the most of others follows the conventional process [48], [49]. It is a part of GxP management. The aspects of validation and verification are even more intense and emphasized if an OOS occurs [50]. Very often under this circumstance, a multiplicated sample analysis is required for conducting the OOS investigation in a testing laboratory.
    • Medical devices The FDA (21 CFR) has validation and verification requirements for medical devices. See guidance: [2], [51], [52], [53]. and ISO 13485
    • Manufacturing process and cleaning validation are compulsory and regulated by the U.S. Food and Drug Administration [10], [54], [55], [56].
    • Food hygiene: example [3]
    • Clinical laboratory medicine: ISO 15198:2004 Clinical laboratory medicine—In vitro diagnostic medical devices—Validation of user quality control procedures by the manufacturer
Main article: Validation (drug manufacture)

See also

Notes and references

  1. ^ Validation Online. "DESIGN QUALIFICATION". Retrieved 17 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  2. ^ Validation Online. "INSTALLATION QUALIFICATION". Retrieved 17 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  3. ^ Validation Online. "OPERATIONAL QUALIFICATION". Retrieved 17 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  4. ^ Validation Online. "PERFORMANCE QUALIFICATION". Retrieved 17 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  5. ^ Analytical & Precision Balance Co. "Welcome". Retrieved 18 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  6. ^ Scientech. "External Calibration". Retrieved 18 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  7. ^ Torres, Rebecca E. (2007). "Replacement Parts-Identical, Suitable, or Inappropriate?". Retrieved 29 March 2008. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  8. ^ AppLabs. "ISV, IHV Certification Programs". Retrieved 26 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  9. ^ AppLabs. "AppLabs attains ISO27001:2005 accreditation". Retrieved 26 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  10. ^ a b c "GUIDELINE ON GENERAL PRINCIPLES OF PROCESS VALIDATION". U.S. Food and Drug Administration. May 1987. Retrieved 12 July 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help) Cite error: The named reference "ggpp" was defined multiple times with different content (see the help page).
  11. ^ Groupe Novasep. "Prospective validation". Retrieved 24 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  12. ^ Quinn, James; et al. (2006). "Prospective Validation of the San Francisco Syncope Rule to Predict Patients With Serious Outcomes". Annals of Emergency Medicine. 47 (5). Elsevier: 448–454. doi:10.1016/j.annemergmed.2005.11.019. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  13. ^ Sangiovanni, A.; et al. (2007). "Prospective validation of AASLD guidelines for the early diagnosis of hepatocellular carcinoma in cirrhotic patients". Digestive and Liver Disease. 40 (5). Elsevier: A22–A23. doi:10.1016/j.dld.2007.12.064. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  14. ^ Germing, U.; et al. (2006). "Prospective validation of the WHO proposals for the classification of myelodysplastic syndromes". Haematologica. 91 (12): 1596–1604. PMID 17145595. Retrieved 24 September 2008. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  15. ^ Sciolla, Rossella; et al. (2008). "Rapid Identification of High-Risk Transient Ischemic Attacks: Prospective Validation of the ABCD Score". Stroke. 39 (2). American Heart Association: 297–302. doi:10.1161/STROKEAHA.107.496612. PMID 18174479. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  16. ^ Pfisterer, Matthias; et al. (2008). "Drug-eluting or bare-metal stents forlarge coronary vessel stenting? The BASKET-PROVE (PROspective Validation Examination) trial: Study protocol and design". American Heart Journal. 115 (4). Mosby-Year Book Inc: 609–614. doi:10.1016/j.ahj.2007.11.011. Retrieved 24 September 2008. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  17. ^ Van Geest-Daalderop, Johanna H. H.; et al. (2008). "Improvement in the regulation of the vitamin K antagonist acenocoumarol after a standard initial dose regimen: prospective validation of a prescription model". Journal of Thrombosis and Thrombolysis. Springer. doi:10.1007/s11239-008-0203-4. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  18. ^ Ames, D.; et al. (1996). "Prospective validation of the EBAS-DEP — A short sensitive screening instrument for depression in the physically ill elderly". European Psychiatry. 11 (Supplement 4, ). Elsevier: 361s. doi:10.1016/0924-9338(96)89148-6. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)CS1 maint: extra punctuation (link)
  19. ^ Kidwell, Chelsea S.; et al. (2000). "Identifying Stroke in the Field: Prospective Validation of the Los Angeles Prehospital Stroke Screen (LAPSS)". Stroke. 31. American Heart Association: 71–76. PMID 10625718. Retrieved 24 September 2008. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  20. ^ U.S. Food and Drug Administration. "Ch. 4 PROCESS VALIDATION in Medical Device Quality Systems Manual". Retrieved 2009-08-06. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  21. ^ Groupe Novasep. "Retrospective validation". Retrieved 24 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  22. ^ Validation-online.net. "Retrospective validation Rationale". Retrieved 24 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  23. ^ Vieth, Erich. "Who changed the Bible and why? Bart Ehrman's startling answers". Retrieved 26 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  24. ^ Arlandson, James M. "Domestic violence in Islam". Retrieved 17 October 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  25. ^ Hart, D. (2007). "Retrospective Validation of a Clinical Decision Rule to Safely Rule Out Subarachnoid Hemorrhage in Emergency Department Headache Patients". Annals of Emergency Medicine. 50 (3): S102–S103. doi:10.1016/j.annemergmed.2007.06.388. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  26. ^ Kluger, Michael D.; et al. "Retrospective Validation of a Surveillance System for Unexplained Illness and Death: New Haven County, Connecticut". Retrieved 26 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  27. ^ Fine, Leon G.; et al. "How to evaluate and improve the quality and credibility of an outcomes database: validation and feedback study on the UK Cardiac Surgery Experience". Retrieved 26 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  28. ^ Department of Health (United Kingdom). "The White Paper Trust, assurance and safety: The regulation of health professionals". Retrieved 30 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  29. ^ Merkur, Sherry. "Physician revalidation in Europe". Royal College of Physicians. Retrieved 30 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  30. ^ Australian Pesticides & Veterinary medicines Authority (2004). "Guidelines for the Validation of Analytical Methods for Active Constituent, Agricultural and Veterinary Chemical Products" (PDF). Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  31. ^ Bressolle, Françoise; et al. (1996). "Validation of liquid chromatographic and gas chromatographic methods Applications to pharmacokinetics". Journal of Chromatography B: Biomedical Sciences and Applications. 686 (1): 3–10. doi:10.1016/S0378-4347(96)00088-6. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  32. ^ Peptisyntha S.A. (2009). "Commercial scale production". Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  33. ^ del Rosario Alemán, María (2007). "Downstream Processing: A Revalidation Study of Viral Clearance in the Purification of Monoclonal Antibody CB.Hep-1". Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  34. ^ El Eman, Khaled; et al. (2009). "Evaluating Predictors of Geographic Area Population Size Cut-offs to Manage Re-identification Risk" (PDF). Journal of the American Medical Informatics Association. 16 (2): 256–266. Retrieved 12 July 2009. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  35. ^ Tollman, Stephen M; et al. (2008). "Implications of mortality transition for primary health care in rural South Africa: a population-based surveillance study". Journal of the American Medical Informatics Association. 372 (9642): 893–901. doi:10.1016/S0140-6736(08)61399-9. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  36. ^ United States Department of Health & Human Services (2009). "Waning Letter (WL No. 320-08-04)" (PDF). Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  37. ^ Health Canada (2004). "Validation Guidelines for Pharmaceutical Dosage Forms (GUIDE-0029)". Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); line feed character in |title= at position 41 (help)
  38. ^ Food and Drug Administration (United States) (May 2001). "Guidance for Industry: Bioanalytical Method Validation" (PDF). Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  39. ^ Health Sciences Authority. "Guidance Notes on Analytical Method Validation: Methodology" (PDF). Retrieved 29 September 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  40. ^ Heyden, Y. Vander; et al. (2001). "Guidance for robustness/ruggedness tests in method validation". Journal of Pharmaceutical and Biomedical Analysis. 24 (5–6). Elsevier: 723–753. doi:10.1016/S0731-7085(00)00529-X. {{cite journal}}: |access-date= requires |url= (help); Explicit use of et al. in: |first= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  41. ^ Ermer, Joachim (2005). Method Validation in Pharmaceutical Analysis: A Guide to best Practice. Wiley-VCH. p. 418. ISBN 3527312552. {{cite book}}: |access-date= requires |url= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  42. ^ "Calibration of dissolution test apparatus (USP apparatus 1 and 2) - SOP". {{cite web}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Missing or empty |url= (help)
  43. ^ Szsz, Gy.; et al. (1998). "Optimized and Validated HPLC Methods for Compendial Quality Assessment. III. Testing of Optical Purity Applying 1-Acid-Glycoprotein Stationary Phase". Journal of Liquid Chromatography & Related Technologies. 21 (16): 2535–2547. doi:10.1080/10826079808003597. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  44. ^ Agilent. "System suitability testing for Aripirazole quality control with the Agilent 1120 Compact LC and ZORBAX C-18 columns" (PDF). Retrieved 29 June 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  45. ^ Li, Yong-guo; et al. (2004). "Ruggedness/robustness evaluation and system suitability test on United States Pharmacopoeia XXVI assay ginsenosides in Asian and American ginseng by high-performance liquid chromatography". Journal of Pharmaceutical and Biomedical Analysis. 35 (5): 1083–1091. doi:10.1016/j.jpba.2004.04.005. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  46. ^ 日本药局方. "Japanese Pharmacopoeia". Retrieved 29 June 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  47. ^ Nash, Robert A.; et al. (2003). Pharmaceutical Process Validation: An International Third Edition. Informa Healthcare. p. 860. ISBN 0824708385. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  48. ^ De Caris, Sandro; et al. "Risk-based equipment qualification: a user/supplier cooperative approach" (PDF). Retrieved 15 June 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  49. ^ Ocampo, Arlene; et al. (2007). "Current challenges for FDA-regulated bioanalytical laboratories for human (BA/BE) studies. Part I: defining the appropriate compliance standards - application of the principles of FDA GLP and FDA GMP to bioanalytical laboratories". The Quality Assurance Journal. 11 (1). John Wiley & Sons: 3–15. doi:10.1002/qaj.399. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  50. ^ "Guidance for Industry: Investigating Out-of-Specification (OOS) Test Results for Pharmaceutical Production" (PDF). Food and Drug Administration (United States). 2006. Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  51. ^ "Guidance for Industry: Cybersecurity for Networked Medical Devices Containing Off-the Shelf (OTS) Software" (PDF). Food and Drug Administration. 14 January 2005. Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  52. ^ "General Principles of Software validation; Final Guidance for Industry and FDA Staff" (PDF). Food and Drug Administration (United States). 11 January 2002. Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  53. ^ "Guidance for Industry and FDA Staff: Medical Device User Fee and Modernization Act of 2002, Validation Data in Premarket Notification Submissions (510(k)s) for Reprocessed Single-Use Medical Devices" (PDF). Food and Drug Administration. 25 September 2006. Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  54. ^ "GUIDE TO INSPECTIONS VALIDATION OF CLEANING PROCESSES". Food and Drug Administration (United States). July 1993. Retrieved 12 July 2009. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  55. ^ Nassani, Mowafak. "Cleaning validation in the pharmaceutical industry". Retrieved 20 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  56. ^ Bharadia, Praful D. "A review of current implementation strategies for validation of cleaning processes in the pharmaceutical industry". Retrieved 20 March 2008. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  57. ^ Masako, Tsujimoto. "Verification of genetic recombination by hypha fusion of Pyricularia oryzas using transducing gene as marker. (the Ministry of Agriculture, Forestry and Fisheries Natl. Agricultural Res. Center S)". Retrieved 20 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help)
  58. ^ Vollmer-Sanders, Carrie Lynn; et al. "Implications of the Voluntary Michigan Agriculture Environmental Assurance Program (MAEAP) Verification on Livestock Operations, 2000-2004". Retrieved 20 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  59. ^ Haboudane, Driss; et al. (2004). "Hyperspectral vegetation indices and novel algorithms for predicting green LAI of crop canopies: Modeling and validation in the context of precision agriculture". Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement. 90 (3). Elsevier: 337–352. doi:10.1016/j.rse.2003.12.013. {{cite journal}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  60. ^ Thorp, Kelly; et al. "USING CROSS-VALIDATION TO EVALUATE CERES-MAIZE YIELD SIMULATIONS WITHIN A DECISION SUPPORT SYSTEM FOR PRECISION AGRICULTURE". Retrieved 20 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  61. ^ Randolph, Susan; et al. "Monitoring the Realization of the Right to Food: Adaptation and Validation of the U.S. Department of Agriculture Food Insecurity Module to Rural Senegal". Retrieved 20 March 2008. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); Explicit use of et al. in: |first= (help)
  62. ^ Pruitt, Kirk. "Method and system for authenticating appraisal reports". Retrieved 15 September 2008. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
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