Penny (United States coin)

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Cent
United States
Value0.01 U.S. dollar
Mass(1982-present) 2.5 g (0.08 troy oz)
Diameter19.05 mm (0.75 in)
Thickness1.52 mm (0.0598 in)
EdgePlain
Composition(1982–present) copper-plated zinc
97.5% Zn, 2.5% Cu
Years of minting1793–1814, 1816–present
Catalog number
Obverse
US One Cent Obv.png
DesignAbraham Lincoln
DesignerVictor D. Brenner
Design date1909 (modified since)
Reverse
US One Cent Rev.png
DesignUnion Shield
DesignerLyndall Bass
Design date2010–present

The United States one-cent coin (symbol: ¢), often called the "penny", is a unit of currency equaling one one-hundredth of a United States dollar. It has been the lowest face-value physical unit of U.S. currency since the abolition of the half-cent in 1857 (the abstract mill, which has never been minted, equal to a tenth of a cent, continues to see limited use in the fields of taxation and finance). The first U.S. cent was produced in 1787, and the cent has been issued primarily as a copper or copper-plated coin throughout its history. Its obverse has featured the profile of President Abraham Lincoln since 1909, the centennial of his birth. From 1959 (the sesquicentennial of Lincoln's birth) to 2008, the reverse featured the Lincoln Memorial. Four different reverse designs in 2009 honored Lincoln's 200th birthday and a new, "permanent" reverse – the Union Shield – was introduced in 2010. The coin is 0.75 inches (19.05 mm) in diameter and 0.0598 inches (1.52 mm) in thickness. Its weight has varied, depending upon the composition of metals used in its production (see further below).

The U.S. Mint's official name for the coin is "cent"[1] and the U.S. Treasury's official name is "one cent piece".[2] The colloquial term penny derives from the British coin of the same name, which occupies a similar place in the British system. Pennies is the plural form (not to be confused with pence, which refers to the unit of currency).

In the early 2010s the price of metal used to make pennies rose to a noticeable cost to the mint which peaked at more than $0.02, a negative seigniorage, for the $0.01 face-value coin. This pushed the mint to look for alternative metals again for the coin, and also brought the debate about eliminating the coin into more focus. There are currently no firm plans to do so.[3]

History of composition[edit]

The composition of the penny has varied over time:[4][5]

Years Material Weight
(grains)
Weight
(grams)
1793–1795 ~100% copper 208 grains 13.48
1795–1857 † ~100% copper 168 grains 10.89
1856–1864 88% copper, 12% nickel (also known as NS-12) 72 grains 4.67
1864–1942 bronze (95% copper, 5% tin and zinc) 48 grains 3.11
1943 zinc-coated steel (also known as 1943 steel cent) 42 grains 2.72
1944–1946 gilding metal (95% copper, 5% zinc) 48 grains 3.11
1947–1962 bronze (95% copper, 5% tin and zinc) 48 grains 3.11
1962 – September 1982 gilding metal (95% copper, 5% zinc) 48 grains 3.11
October 1982 – present copper-plated zinc (97.5% zinc, 2.5% copper) 38.6 grains 2.5

The isotope composition of early coins spanning the period 1828 to 1843 reflects the copper from Cornish ores from England, while coins after 1850 reflect the Keweenaw Peninsula, Michigan ores, a finding consistent with historical records.[6]

In 1943, at the peak of World War II, zinc-coated steel cents were made for a short time because of war demands for copper. A few copper cents from 1943 were produced from 1942 planchets remaining in the bins. Similarly, some 1944 steel cents have been confirmed. From 1944 to 1946, salvaged ammunition shells made their way into the minting process, and it was not uncommon to see coins featuring streaks of brass or having a considerably darker finish than other issues.

During the early 1970s, the price of copper rose to the point where the cent contained almost one cent's worth of copper. This led the Mint to test alternative metals, including aluminum and bronze-clad steel. Aluminum was chosen, and over 1.5 million samples of the 1974 aluminum cent were struck before ultimately being rejected.

The cent's composition was changed in 1982 because the value of the copper in the coin started to rise above one cent.[7] Some 1982 pennies used the 97.5% zinc composition, while others used the 95% copper composition. With the exception of 2009 bicentennial cents minted specifically for collectors, United States cents minted after 1982 have been zinc with copper plating. The bronze and copper cents can be distinguished from the newer zinc cents by dropping the coins on a solid surface. The predominantly zinc coins make a lower-pitched "clunk", while the copper coins produce a higher-pitched ringing sound.[8] In addition, a full 50-cent roll of pre-1982/3 coins weighs 5.4 oz (150 g) compared to a post-1982–83 roll which weighs 4.4 oz (120 g).

Designs[edit]

The coin has gone through several designs over its two-hundred-year time frame. Until 1857 it was about the size of the current U.S. dollar coins (Susan B. Anthony through present dollars). Shown below are the different cent designs that have been produced; mintage figures can be found at United States cent mintage figures.

Large cents:

Small cents:

Throughout its history, the Lincoln cent has featured several typefaces for the date, but most of the digits have been old-style numerals, except with the 4 and 8 neither ascending nor descending. The only significant divergence is that the small 3 was non-descending (the same size as a 0, 1, or 2) in the early history, before switching to a descending, large 3 for the year 1934 and then permanently (as of 2014) in 1943. Similarly, the digit 5 was small and non-descending up to 1945.

Lincoln cent[edit]

The Lincoln cent is the current one-cent coin of the U.S. It was adopted in 1909 (which would have been Lincoln's 100th birthday), replacing the Indian Head cent. Its reverse was changed in 1959 from a wheat-stalks design to a design which includes the Lincoln Memorial (to commemorate Lincoln's sesquicentennial) and was replaced again in 2009 with four new designs to commemorate Lincoln's bicentennial. There are more one-cent coins produced than any other denomination, which makes the Lincoln cent a familiar item. In its lifespan, this coin has weathered both world wars, one of which temporarily changed its composition as part of the war effort. The obverse design is the longest produced for any circulating American coin.

History[edit]

A collection of Lincoln cents from 1941 to 1974. Nearly complete set in a folder. Also features two error coins.
Reverses of the Lincoln cent
Wheat (1909–1958)
Lincoln Memorial (1959–2008)
Birth and early childhood in Kentucky (Lincoln Bicentennial, 2009)
Formative Years in Indiana (Lincoln Bicentennial, 2009)
Professional life in Illinois (Lincoln Bicentennial, 2009)
Presidency in DC (Lincoln Bicentennial, 2009)
Union shield (2010–present)

When the Lincoln one-cent coin made its initial appearance in 1909, it marked a radical departure from the accepted styling of United States coinage, as it was the first regular coin to bear a portrait other than the mythical Liberty which appeared on most pre-1909 regular coins. Previously, a strong feeling had prevailed against using portraits on coins in the United States, but public sentiment stemming from the 100th anniversary celebration of Abraham Lincoln's birth proved stronger than the long-standing tradition.

A variety of privately minted tokens bearing Lincoln's image circulated as one-cent pieces during Lincoln's presidency; legitimate coinage had become scarce during the Civil War. These early tokens undoubtedly influenced the denomination, appearance, size, and composition of Lincoln cents.

Theodore Roosevelt, the 26th U.S. president, thought American coins were so common and uninspiring that he attempted to get the motto "In God We Trust" removed as offending religion. Roosevelt had the opportunity to pose for a young Lithuanian-born Jew, Victor David Brenner, who, since arriving nineteen years earlier in the United States had become one of the nation's premier medalists. Roosevelt had learned of Brenner's talents in a settlement house on New York City's Lower East Side and was immediately impressed with a bas-relief that Brenner had made of Lincoln, based on a Mathew Brady photograph. Roosevelt, who considered Lincoln the savior of the Union and the greatest Republican president, and who also considered himself Lincoln's political heir, ordered the new Lincoln cent to be based on Brenner's work and to be released just in time to commemorate Lincoln's 100th birthday in 1909. The likeness of President Lincoln on the obverse of the coin is an adaptation of a plaque Brenner created several years earlier which had come to the attention of President Roosevelt in New York.[10]

In addition to the prescribed elements on U.S. coins—LIBERTY and the date—the motto In God We Trust appeared for the first time on a coin of this denomination. The United States Congress passed the Act of March 3, 1865, authorizing the use of this motto on U.S. coins,[11] during Lincoln's tenure in office.

Even though no legislation was required for the new design, approval of the Secretary of the Treasury was necessary to make the change. Franklin MacVeagh gave his approval on July 14, 1909, and not quite three weeks later, on August 2, the new coin was released to the public.

In 1918, after the controversy over Brenner's name and initials on the reverse had died down, his initials were placed on the obverse with no further controversy. They are to be found in minute form on the rim of the bust, just under the shoulder of Lincoln.

Wheat cent (1909–1958)[edit]

A study of three potential reverses resulted in the approval of a very simple design bearing two wheatheads in memorial style. Between these, in the center of the coin, are the denomination and UNITED STATES OF AMERICA, while curving around the upper border is the national motto, E Pluribus Unum, Latin for "Out of Many, One".

The original model bore Brenner's name on the reverse, curving along the rim below UNITED STATES OF AMERICA. Before the coins were issued, however, the initials "VDB" were substituted because officials at the United States Mint felt the name was too prominent. After the coin was released, many protested that even the initials were conspicuous and detracted from the design. Because the coin was in great demand, and because to make a change would have required halting production, the decision was made to eliminate the initials entirely.

Thus in 1909 the U.S. had six different cents: the 1909 and 1909-S Indian Head cents, and four Lincoln coins: 1909 VDB, 1909-S VDB, 1909 and 1909-S. In all cases the Philadelphia mintages far exceeded the San Francisco issues. While the smallest mintage is the '09-S Indian, the '09-S VDB is the key Lincoln date, and hence is most valuable. Its mintage of 484,000 is only 1.7% of the plain V.D.B.

Lincoln Memorial cent (1959–2008)[edit]

Detail of reverse showing Lincoln statue inside the memorial

On February 12, 1959, a revised reverse design was introduced as part of the 150th anniversary of Lincoln's birth. No formal competition was held. Frank Gasparro, then Assistant Engraver at the Philadelphia Mint, prepared the winning entry, selected from a group of 23 models that the engraving staff at the Mint had been asked to present for consideration. Again, only the approval of the Secretary of the Treasury was necessary to make the change because the design had been in use for more than the required 25 years. The imposing marble Lincoln Memorial provides the central motif, with the legends E Pluribus Unum and UNITED STATES OF AMERICA completing the design, together with the denomination. The initials "FG" appear on the right, near the shrubbery. This series is noteworthy for having the image of Abraham Lincoln both on the obverse and reverse, as his likeness can be discerned at the center of the memorial on the reverse.

Lincoln Bicentennial cents (2009)[edit]

The Presidential $1 Coin Act of 2005 required that the cent's reverse be redesigned in 2009. This resulted in the mintage of four different coins showing scenes from Abraham Lincoln's life in honor of the bicentennial of his birth.

These four designs, unveiled September 22, 2008 at a ceremony held at the Lincoln Memorial on the National Mall in Washington, D.C., are:

  • Birth and early childhood in Kentucky: this design features a log cabin and Lincoln's birth year 1809. It was designed by Richard Masters and sculpted by Jim Licaretz. This cent was released into circulation on Lincoln's 200th birthday, February 12, 2009, at a special ceremony at LaRue County High School in Hodgenville, Kentucky, Lincoln's birthplace.[12] The mintage was extremely low compared to prior years (see Lincoln cent mintage figures). It has been nicknamed the "Log Cabin Penny".
  • Formative years in Indiana: this design features a young Lincoln reading while taking a break from rail splitting. It was designed and sculpted by Charles Vickers. Nicknamed the "Indiana Penny", it was released on May 14, 2009.[13]
  • Professional life in Illinois: this design features a young professional Lincoln standing before the Springfield Illinois State Capitol. It was designed by Joel Iskowitz and sculpted by Don Everhart. Nicknamed the "Illinois Penny", it was released on August 13, 2009.[13]
  • Presidency in Washington, D.C.: this design features the half-completed Capitol dome. It was designed by Susan Gamble and sculpted by Joseph Menna. This fourth cent was released to the public on November 12, 2009.[13] U.S. Mint released collector's sets containing this design in copper prior to the public launch of this design in zinc.

Special 2009 cents struck for sale in sets to collectors had the metallic copper content of cents minted in 1909 (95% copper, 5% tin and zinc).[14] Those struck for circulation retained the normal composition of a zinc core coated with copper.

Union shield cent (2010–present)[edit]

The 2005 act that authorized the redesign for the Bicentennial stated that another redesigned reverse for the Lincoln cent will be minted which "shall bear an image emblematic of President Lincoln's preservation of the United States of America as a single and united country".[15] Eighteen designs were proposed for the reverse of the 2010 cent.[16] On April 16, 2009 the Commission of Fine Arts (CFA) met and selected a design that showed 13 wheat sheaves bound together with a ring symbolizing American unity as one nation.[17] Later this design was withdrawn because it was similar to coinage issued in Germany in the 1920s.[18] The Citizens Coinage Advisory Committee later met and chose a design showing a Union shield with ONE CENT superimposed in a scroll; E Pluribus Unum was also depicted in the upper portion of the shield.[18][19] In June 2009 the CFA met again and chose a design featuring a modern rendition of the American flag.[20] As a part of the release ceremony for the last of the 2009 cents on November 12, the design for the 2010 cent was announced.[21] The design chosen was the one that was chosen earlier by the CCAC.[21] According to the Mint, the 13 stripes on the shield "represent the states joined in one compact union to support the Federal government, represented by the horizontal bar above".[22] The Mint also noted that a shield was commonly used in paintings in the Capitol hallways painted by Constantino Brumidi, an artist in the Capitol active during the Lincoln Presidency.[22] The obverse of the cent was also changed to a modern rendition of Brenner's design.[23][21] The new Union Shield design replaces the Lincoln memorial in use since 1959.[21] The coin was designed by artist Lyndall Bass and sculpted by U.S. Mint sculptor-engraver Joseph Menna.[24] In January 2010, the coins were released early in Puerto Rico;[25] this was caused by a shortage of 2009-dated pennies on the island.[23] The new design was released at a ceremony at the Abraham Lincoln Presidential Library in Springfield, Illinois on February 11, 2010.[26] In 2017, cents minted in Philadelphia were struck with a "P" mintmark to celebrate the 225th anniversary of the U.S. Mint. 2017 is the only year that Philadelphia cents have had a mintmark.[27]

Production issues[edit]

Proposals to eliminate[edit]

It has been suggested that the cent should be eliminated as a unit of currency for several reasons including that many Americans do not actually spend them, but rather only receive them in change at stores and proceed to return them to a bank for higher denomination currencies, or cash them in at coin counting kiosks. Most modern vending machines do not accept pennies, further diminishing their utility, and the production cost (figured in U.S. Dollars) now exceeds the face value of the coin, caused by increasing inflation.[28] In 2001 and 2006, for example, United States Representative Jim Kolbe (R) of Arizona introduced bills which would have stopped production of pennies (in 2001, the Legal Tender Modernization Act, and in 2006, the Currency Overhaul for an Industrious Nation [COIN] Act).[29]

In anticipation of the business of melting down U.S. pennies and U.S. nickels for profit, the U.S. Mint, which is a part of the US Department of the Treasury, implemented new regulations[30] on December 14, 2006, which criminalize the melting of pennies and nickels and place limits on export of the coins. Violators can be punished with a fine of up to $10,000 USD and/or imprisoned for a maximum of five years.[31]

Metal content and manufacturing costs[edit]

The price of metal drives the cost to manufacture a cent. The Secretary of the Treasury has authority to alter the percentage of copper and zinc in the one-cent coin if needed due to cost fluctuations.[32]

For years, the Mint's production and shipping costs for cents have exceeded the face value of the coin (the Mint's fixed costs and overhead, however, are absorbed by other circulating coins).[33] In fiscal year 2010, each cent cost 1.79 cents to produce and ship.[32] After reaching a peak cost of 2.41 cents in 2011, the cost declined to 2.00 cents in 2012,[34] 1.83 cents in 2013,[35] 1.70 cents in 2014,[36] 1.67 cents in 2015,[37] and 1.50 cents in 2016.[38] It then rose again: 1.82 cents in 2017, 2.06 cents in 2018,[39] and 1.99 cents in 2019.[40]

As a result, the U.S. Treasury loses millions of dollars every year producing cents. For example, the loss in 2013 was $55 million.[35]

When copper reached a record high in February 2011,[41] the melt value of a 95% copper cent was more than three times its face value. As of January 21, 2014, a pre-1982 cent contained 2.20325 cents' worth of copper and zinc, making it an attractive target for melting by people wanting to sell the metals for profit. In comparison, post-1982 copper-plated zinc cents have a metallurgical value of only 0.55152 cents.[42]

Toxicity[edit]

Zinc, a major component of U.S. cents minted after mid-1982, is toxic in large quantities. Swallowing such a coin, which is 97.5% zinc, can cause damage to the stomach lining because of the high solubility of the zinc ion in the acidic stomach.[43] Coins are the most commonly ingested foreign body in children but generally are allowed to pass spontaneously unless the patient is symptomatic.[44] Zinc toxicity, mostly in the form of the ingestion of U.S. pennies minted after 1982, is commonly fatal in dogs where it causes a severe hemolytic anemia.[45] It is also highly toxic in pet parrots and can often be fatal.[46]

See also[edit]

References[edit]

  1. ^ "The United States Mint Coin Specifications". Washington, D.C.: United States Mint. Retrieved 2009-11-09. Denomination:Cent; Nickel; Dime; Quarter Dollar.... (categories across the top of the specifications chart)
  2. ^ "Denominations". Washington, D.C.: United States Department of the Treasury. Retrieved 2015-03-03. The proper term is "one cent piece," but in common usage this coins is often referred to as a penny or cent.
  3. ^ Nicks, Denver (2016-04-20). "Get Rid of the Penny? Treasury Secretary Jacob Lew Says Yes | Money". Time.com. Archived from the original on April 24, 2016. Retrieved 2018-04-24.
  4. ^ "Coin Specifications". Retrieved 2019-03-23.
  5. ^ U.S. Mint (3 September 2019). "Coin Production". Retrieved 2020-12-20.
  6. ^ Mathur, R (2009). "The history of the United States cent revealed through copper isotope fractionation". Journal of Archaeological Science. 36 (2): 430–433. doi:10.1016/j.jas.2008.09.029.
  7. ^ "1982 Lincoln Memorial Cents". Coins.thefuntimesguide.com. Retrieved 2011-07-20.
  8. ^ "Is my Penny a Copper, or a Zinc Cent?". Retrieved 2008-06-16.
  9. ^ "The United States Mint Coins and Medals Program". USMint.gov. Retrieved 2010-12-27.
  10. ^ Margolick, David (2007-02-11). "Penny Foolish". The New York Times. Retrieved 2010-05-22.
  11. ^ "History of 'In God We Trust'". treasury.gov. Retrieved 2016-04-29.
  12. ^ Kocher, Greg (February 13, 2009). "Lincoln's birthplace is launch site for new penny". Lexington Herald-Leader.
  13. ^ a b c O'Keefe, Ed (February 17, 2009). "Heads Abe, Tails New On Pennies Marking Lincoln Bicentennial". The Washington Post. p. A11.
  14. ^ "U.S. Mint Online Product Catalog". Catalog.usmint.gov. Retrieved 2011-07-20.
  15. ^ Pub.L. 109–145 (text) (pdf), 119 Stat. 2674, enacted December 22, 2005 – Presidential $1 Coin Act of 2005, Title VI, §303. "The design on the reverse of the 1-cent coins issued after December 31, 2009, shall bear an image emblematic of President Lincoln's preservation of United States of America as a single and united country." Retrieved 2009-11-30.
  16. ^ Staff (2009-06-09). "2010 Lincoln Cent Design Proposals". 2010 Lincoln Cents. Retrieved 2009-11-30. There were initially 18 design proposals for the 2010 Lincoln Cent reverse.
  17. ^ McAllister, Bill (2009-05-04). "Wheat Design may appear on the 2010 cent". Coin World. 50 (2560): 1.
  18. ^ a b McAllister, Bill (2009-05-18). "Mint withdraws 2010 'Wheat' cent design". Coin World. 50 (2562): 1.
  19. ^ McAllister, Bill (2009-05-18). "Mint withdraws 2010 'Wheat' cent design". Coin World. 50 (2562): 1.
  20. ^ McAllister, Bill (2009-05-18). "Commission votes for U.S. flag on 2010 1¢". Coin World. 50 (2565): 1.
  21. ^ a b c d Gilkes, Paul (2009-11-30). "Cent to bear Union Shield design in 2010". Coin World. 50 (2590): 1, 68.
  22. ^ a b "United States Mint Releases Fourth 2009 Lincoln Bicentennial One-Cent Coin" (Press release). United States Mint. 2009-11-12. Retrieved 2009-11-30.
  23. ^ a b Gilkes, Paul (2010-02-15). "Mint Returns to 1909 Galvano for Portrait". Coin World. 51 (2601): 1, 24.
  24. ^ "United States Mint Launches 2010 Lincoln One-Cent Coin" (Press release). United States Mint. 2010-02-11. Retrieved 2010-02-11. The reverse of the 2010 and beyond Lincoln cent was designed by United States Mint Artistic Infusion Program Associate Designer Lyndall Bass and executed by United States Mint Sculptor-Engraver Joseph Menna.
  25. ^ Gilkes, Paul (2010-02-08). "First Circulation Reports of 2010 Cents From Puerto Rico". Coin World. 51 (2600): 5.
  26. ^ Ruston, Bruce (2010-02-11). "Collectors seek to turn profit on pennies". State Journal-Register. Archived from the original on 2010-02-14. Retrieved 2010-02-11. The newest—and for now permanent—version of the Lincoln penny was unveiled this morning at the Abraham Lincoln Presidential Museum...CS1 maint: bot: original URL status unknown (link)
  27. ^ McMorrow-Hernandez, Joshua (16 January 2017). "Philadelphia Mint Quietly Releases 2017-P Lincoln Cent". coinweek.com.
  28. ^ Hagenbaugh, Barbara (2006-05-09). "Coins cost more to make than face value". USA Today. Retrieved 2006-10-04.
  29. ^ Zappone, Christian (July 18, 2006). "Kill-the-penny bill introduced". CNN.
  30. ^ "United States Mint Moves to Limit Exportation & Melting of Coins". Usmint.gov. Retrieved 2011-07-20.
  31. ^ "CFR 2010 title31 vol1 part82" (PDF). U.S. Government Printing Office. Retrieved 2013-01-05.
  32. ^ a b United States Mint (2010-12-04). "U.S. Mint 2010 Annual Report" (PDF). Retrieved 2011-01-16.
  33. ^ Staff (April 17, 2012). "Statement of Rodney J. Bosco Navigant Consulting, Inc. on "The Future of Money: Coin Production"" Before the House Financial Services Subcommittee on Domestic Policy & Technology United States House of Representatives – April 17, 2012" (PDF). U.S. Congress. Retrieved September 10, 2012.
  34. ^ Unser, Mike (2019-05-24). "Penny Costs 2.06 Cents to Make in 2018, Nickel Costs 7.53 Cents; US Mint Realizes $321.1M in Seigniorage". Coin News. Retrieved 2020-07-11.
  35. ^ a b "US Mint Cost To Make Penny and Nickel Declines in FY 2013". January 20, 2014.
  36. ^ "About | U.S. Mint" (PDF). Usmint.gov. Retrieved 2018-04-24.
  37. ^ "US Mint Cost To Make Penny".
  38. ^ Unser, Mike (2017-02-21). "Penny Costs 1.5 Cents to Make in 2016, Nickel Costs 6.32 Cents; US Mint Realizes $578.7M in Seigniorage". Coin News. Retrieved 2020-07-11.
  39. ^ Unser, Mike (2019-05-24). "Penny Costs 2.06 Cents to Make in 2018, Nickel Costs 7.53 Cents; US Mint Realizes $321.1M in Seigniorage". Coin News. Retrieved 2020-07-11.
  40. ^ Unser, Mike (2020-02-07). "Penny Costs 1.99 Cents to Make in 2019, Nickel Costs 7.62 Cents; US Mint Realizes $318.3M in Seigniorage". Coin News. Retrieved 2020-07-11.
  41. ^ "METALS-Copper falls on euro zone disappointment, China worry". Reuters. 2012-08-20. Retrieved 2012-11-18.
  42. ^ "Current Melt Value Of Coins – How Much Is Your Coin Worth?". Coinflation.com. Retrieved 2014-01-21.
  43. ^ Dawn N. Bothwell, M.D., and Eric A. Mair, M.D., FAAP. Chronic Ingestion of a Zinc-Based Penny, Pediatrics Vol. 111, No. March 3, 2003, pp. 689–691. Retrieved 2008-04-17.
  44. ^ Mark L. Waltzman, M.D. [1] Current Opinion in Pediatrics Vol. 45, No. 1 Jan.–Feb., 2006, pp.71–3. Retrieved 2010-02-23.
  45. ^ Stowe CM, Nelson R, Werdin R, et al.: Zinc phosphide poisoning in dogs. JAVMA 173:270, 1978
  46. ^ See, for example, this list of common parrot illnesses and their causes

External links[edit]