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Quadripoint

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A quadripoint is a point on the Earth that touches the border of four distinct territories.[1][2] The term has never been in common use—it may not have been used before 1964, by the Geographer of the United States.[3][n 1] The word does not appear in the Oxford English Dictionary or Merriam-Webster Online dictionary, but it does appear in the Encyclopædia Britannica,[4] and the World Factbook articles on Botswana, Namibia, Zambia, and Zimbabwe, dating back to 1990.[5]

History

The borders of the historic condominium of Moresnet. Moresnet is colored blue, the Netherlands orange, Belgium yellow, and Prussia green.
Zambezi River at the junction of Namibia (top left), Zambia (top), Zimbabwe (bottom right) and Botswana (bottom left)

An early instance of four political divisions meeting at a point is in England (attested in the Domesday Book, 1086,[6][7] and mentioned since 969 if not 772[8]); it combined until 1931 the English shires/counties of Gloucester, Oxford, Warwick and Worcester. But another ancient four county point between Warwick, Derby, Leicester and Stafford could be slightly older, as it is associated with a Mercian stone in No Man's Heath, Warwickshire.

The earliest known quadripoint involving modern nation states existed from 1817 to 1821 where the present Alabama-Mississippi state line crossed the 31st parallel border between Spain and the United States. During that period, the part of West Florida between the Pearl and Perdido rivers (which Spain still owned but the United States forcibly occupied and annexed in 1810 after belatedly claiming it as part of the Louisiana Territory purchased from France in 1803) was subdivided and allocated partly to the State of Mississippi and partly to the Territory (and later State) of Alabama. There resulted, at the intersection of demarcated boundaries, an international quadripoint of four territories, which in the United States were named (clockwise) Baldwin and Mobile Counties of Alabama and Jackson and Greene Counties of Mississippi, though Mobile and Jackson Counties were actually still in Spain.[9][10][11]

Between 1830 and 1920 there was a quadripoint at the convergence of Belgium, Prussia/Germany, the Netherlands, and Moresnet. 50°45′N 6°01′E / 50.75°N 6.02°E / 50.75; 6.02 (former quadripoint)[12] Moresnet was never truly a country but rather only a neutral territory or condominium of the Netherlands and Prussia (originally), and of Belgium and Germany (ultimately). Subsequent political changes have restored its quadripartition along municipal lines (Kelmis, Plombieres within Belgium) since 1976 (though it has also enjoyed fivefold partition along municipal lines at times).

Four-country quadripoints

Many sources claim that a quadripoint exists in Africa, where the borders of Namibia, Botswana, Zambia, and Zimbabwe come together at the confluence of the Cuando (also called Chobe) and Zambezi rivers (approximately 17°47′30″S 25°15′48″E / 17.79167°S 25.26333°E / -17.79167; 25.26333).[13][14][15] Ever since the boundaries in the area were defined around the turn of the 20th-century there was uncertainty about whether they met to form a single quadripoint in the Zambezi River, or whether they met in two tripoints in the river, close but not quite touching. If there was a quadripoint, then Botswana and Zambia would not share a border, except at a single point.

There have been a few international incidents revolving round that particular quadripoint. In 1970, South Africa informed Botswana that there was no common border between Botswana and Zambia, claiming that a quadripoint existed. As a result, South Africa claimed, the Kazungula Ferry, which links Botswana and Zambia at the quadripoint, was illegal. Botswana firmly rejected both claims. There was actually a confrontation and shots were fired at the ferry[16]; some years later, the Rhodesian Army attacked and sank the ferry, maintaining that it was serving military purposes.

The question of whether a quadripoint exists there, remains unresolved. Ian Brownlie, who studied the case, determined that the possibility of a quadripoint, although unlikely, cannot be definitively ruled out. To resolve the issue all four states, Botswana, Namibia, Zambia, and Zimbabwe would have to conduct precise boundary surveys.[1]

However a true four-country point did formerly exist in Africa -- indeed (if we exclude Kazungula) the only quadricountry quadripoint which the world has definitely known[citation needed] -- for a period of 8 months during 1960 and 1961, at the location, in southern Lake Chad, of the present Cameroun-Chad-Nigeria tripoint, where the latter three countries were then also joined by a territory called Northern Cameroons which still belonged, under United Nations mandate, to the United Kingdom, until it was finally annexed to Nigeria.[citation needed]

Quadripoints within and between nations

A map of southeastern Nebraska, from about Gage County to Hall County, showing county lines in black and PLSS township lines in purple. In many parts of the United States county lines are based on PLSS townships and sections. There are occasional jogs in the grid, due to correction lines.

Quadripoints can exist at the meeting of political subdivisions of any type(s) or level(s). The most common are in the United States and Canada, where the grid-based Public Land Survey System (PLSS) and Dominion Land Surveys (DLS), respectively, resulted in a large number of quadripoints at the corners of survey units such as DLS townships, PLSS townships, sections, and various other gridded subdivisions. The borders of U.S. counties and towns are often defined by survey townships. There are dozens of quadripoints between U.S. counties, hundreds between U.S. municipalities, and indeed thousands (of usually bilateral ones) on the edges of checkerboard-patterned Indian reservations and other federally reserved territories. But of all the quadripoints that exist, the most noted are about 10 international instances, and about 10 others of primary national subdivisions (such as provinces or states).

Among the international quadripoints (examples below) a few general types can be distinguished. In the absence of four-country points, three-country quadripoints are perhaps most significant. These combine two divisions of one country with (one each of) two other countries. But there also exist merely binational quadripoints -- of several varieties. Some of these combine two subdivisions of two countries, others three subdivisions of one country with (one of) another; while still others occur at points where international boundaries appear to touch or cross themselves -- with or without subdivision -- or where an international boundary appears to bifurcate around disputed territories.

Also below, by country, some quadripoints composed only of primary subdivisions.

Argentina

The Argentine provinces of La Pampa, Río Negro, Mendoza and Neuquén may meet at 37°34′00″S 68°14′00″W / 37.56667°S 68.23333°W / -37.56667; -68.23333. Rio Negro has disputed this since a 1966 resurvey cast the exact boundary convergence into some doubt. [citation needed]

Austria/Germany

On the summit of Sorgschrofen peak, the international boundary touches (or crosses) itself at marker number 110, where two Austrian (Tyrolean: Reutte) and two German (Bavarian: Obergallau, Ostgallau) municipalities meet at a quadripoint established politically in 1844, cadastrally 1342 or earlier: (in clockwise order) Jungholz AT, Pfronten DE, Schattwald AT and Bad Hindelang DE.[17][18]

Bangladesh/India

The international boundary touches (or crosses) itself at one (or possibly two) locations shared by India (West Bengal state, Cooch Behar district) and Bangladesh (Rangpur Division, Lalmonirhat district). A well documented instance occurs in Mekhliganj subdivision and a less definite one in Mathabhanga subdivision (of Cooch Behar), both involving Patgram subdivision (of Lalmonirhat). Additional political subdivision does not appear to result in either case. Its (or their) international stature has been intermittent since Mughal times and is presently owing to the Radcliffe Award of 1947.[19][20]

The international boundaries in Baarle between Belgium (dark yellow) and Netherlands (pale yellow), with several bi-national quadripoints, as well as enclaves and exclaves.

Belgium/Netherlands

The international boundary touches (or crosses) itself, without imparting political subdivision, within the commingled municipalities of Baarle-Nassau (North Brabant, Netherlands) and Baarle-Hertog (Antwerp, Belgium). The peculiar situation has existed at least cadastrally since about 1198, but its current international distinction dates only from 1830.[21][22] (Tho there are believed and often said to be several such locations in Baarle, there is in fact only one, at the corner indicated H2 on the map at right.)

Canada

The creation of the Canadian territory of Nunavut might have resulted in the creation of a quadripoint between the provinces of Saskatchewan and Manitoba and the territories of Nunavut and Northwest Territories (NWT). Nunavut was officially separated from the Northwest Territories in 1999, though the boundaries had been defined in 1993 via the Nunavut Act and the Nunavut Land Claims Agreement. Both documents define Nunavut's boundary as including the intersection of 60°00'N latitude with 102°00'W longitude, being the intersection of the Manitoba, Northwest Territories and Saskatchewan borders. However, the northernmost point of the Manitoba–Saskatchewan border as surveyed is slightly off from 60° north 102° west, therefore the laws are not perfectly clear about whether the Nunavut–NWT boundary, which has not been surveyed, is to meet the others in a quadripoint or not.[23][24][n 2]

Canada/United States of America

Both of the only known international quadripoints in the Western Hemisphere occur on the Canadian-American border along remote mountain crests. One, which joins the Canadian provinces of Alberta (Improvement District Number 4) and British Columbia (Regional District of East Kootenay) with the Montana counties of Flathead and Glacier where the 49th parallel crosses the Continental Divide also unites an international peace park comprising national parks of both countries (Waterton Lakes and Glacier, respectively). It has been a politically important and precisely stipulated international boundary point since 1818; has been monumented since 1876 (presently by a hollow metallic obeliskoid marker numbered 272); and has maintained a quadripartite status since 1893.[27][28][29][30] The other of the pair occurs in the international boundary sector known as the Highlands, on the ridge separating the Gulf of Saint Lawrence watershed from the Gulf of Maine watershed, where three minor civil divisions of the state of Maine -- namely Dennistown Plantation and Forsyth and Sandy Bay Townships, all in Somerset County -- meet Le Granit Regional County Municipality of the province of Quebec. This quadripoint, which was legally delimited in 1873 and validated in 1895, is marked (like all the corners of the minor civil divisions of Maine) by a brightly painted 8-foot wooden pole.[31][32][33][34]

Croatia/Hungary/Serbia

At a delimitation point determined partly following World War I and partly following World War II, and indirectly monumented by international pillars 415 and 420 on respective riverbanks, there is on the thalweg (center of downstream navigation channel) of the Danube a trinational quadripoint, where the Hungarian counties of Baranya and Bacs-Kiskun meet the Croatian county of Osjecko-Baranjska and the Serbian (Vojvodina) District of West Baka in practical fact (though Croatia continues to claim its former Yugoslav cadastral territory east of the Danube, leaving the quadripoint technically unsettled).[35][36]

Lithuania/Poland/Russia

At 54°21′52″N 22°47′32″E / 54.36435°N 22.79228°E / 54.36435; 22.79228, there is a trinational quadripoint: to the northwest is Russia (specifically the Russian exclave Kaliningrad Oblast); to the northeast Lithuania; and to the southwest and southeast two Voivodships (provinces) of Poland: Warmian-Masurian Voivodship and Podlaskie Voivodeship. [1] The quadripoint exists thanks to the way the border between Poland and Russian SFSR was defined in 1945 by the Potsdam Agreement. The new border between Poland and the USSR bisected Germany's former province of East Prussia; the northern part became Kaliningrad Oblast, and most of the southern part is now Warmia-Masuria.[citation needed]

Mexico

In Mexico there is only one precise quadripoint at 24°33′00″N 100°48′00″W / 24.55000°N 100.80000°W / 24.55000; -100.80000. The "Mojonera de los cuatro estados" ("Four State Boundary Stone") was built to mark the point where Coahuila, Nuevo Leon, San Luis Potosi and Zacatecas states effectively meet.[citation needed]

Norway/Sweden

On the border of Sweden and Norway, there is a binational quadripoint where two Counties of Norway, Nord-Trøndelag and Nordland, meet two Counties of Sweden, Västerbotten and Jämtland, at international boundary marker number 204.[37][38] Though the marker dates from 1760, the point became a quadripoint in the 19th century and became international upon the dissolution of Sweden and Norway in 1905.[39][40]

Oman/Saudi Arabia/Yemen

Amid the Empty Quarter of Arabia -- as trilaterally agreed and monumented in 2006 precisely at the intersection of the 19th parallel and 52nd meridian (datum uncertain) -- Oman (governorate of Dhofar) and Saudi Arabia (emirate of Ash Sharqiyah) meet Yemen (and its governorates of Al Mahrah and Hadramawt), in a tricountry quadripoint.[41][42]

United Kingdom

Due to changes to the borders and numbers of administrative counties in the last century (see Administrative counties of England), no true quadripoint remains in the United Kingdom.

But quite apart from the few shire/county quadripoints that have actually existed in England (see History, above), mistaken claims of an extant one are sometimes made about a place near Stamford where Rutland, Lincolnshire, Cambridgeshire and Northamptonshire seem to meet at a point. (52°38′25″N 0°29′40″W / 52.64028°N 0.49444°W / 52.64028; -0.49444) However, the location actually consists of two tripoints around 66 ft (20 metres) apart.[43]

United States of America

The boundary marker inscribed at the center of the Four Corners Monument, the only state quadripoint in the United States; where Arizona, Utah, Colorado and New Mexico meet.

The Four Corners Monument is the only point in the United States of America where four states meet: Colorado, Utah, New Mexico, and Arizona meet at right angles. The United States first acquired the area now called Four Corners from Mexico after the Mexican American War in 1848. In 1863 Congress created Arizona Territory from the western part of New Mexico Territory. The boundary was defined as a line running due south from the southwest corner of Colorado Territory, which had been created in 1861. By defining one boundary as starting at the corner of another Congress ensured the eventual creation of four states meeting at a point, regardless of the inevitable errors of boundary surveying.[44] The monument is centered at 36°59′56.31532″N 109°02′42.62019″W / 36.9989764778°N 109.0451722750°W / 36.9989764778; -109.0451722750.[45]

Apparent national-level quadripoints

On best available maps, a few additional countries show every appearance of producing one or more quadripoints of their primary subdivisions. These occurrences (neither positively confirmed nor confuted by evidence) are as follows:

  • Andorra: Parishes of Canillo, Encamp, La Messana and Ordino (Michelin zoomable, et al., in legal controversy as of 2003).
  • Bulgaria: Oblasts of Gabrovo, Lovech, Plovdiv and Stara Zagora (large-scale Soviet topo, et al., at Zelenikovets Peak).
  • Dominican Republic: Provinces of Baoruco, Elias Pina, Independencia and San Juan (large-scale American topo, et al., apparently at ridge crossing peak named Gajo de los Magueyes but possibly indefinite).
  • Gabon: Provinces of Moyen-Ogooue, Ngounie, Ogooue-Ivindo and Ogooue-Lolo (large-scale French topo, et al., evidently at an unnamed ridge junction summit).
  • Jamaica: Parishes of Clarendon, Manchester, Saint Ann and Trelawney (American mapping, et al., and local testimony).
  • Libya: Districts of Al Jfara, Bani Walid, Mizdah and Tarhuna Wa Msalata (conventional mapping and local assertion).
  • Mauritania: Regions of Adrar, Brakna, Tagant and Trarza (definitive French map evidence since colonial times).
  • Oman: Governorates of Ad Dakhliyah, Al Batinah, Ash Sharqiyah and Muscat (while not all maps agree).
  • St. Kitts-Nevis: St. Kitts Parishes of St. Anne Sandy Point, St. John Capisterre, St. Paul Capisterre and St. Thomas Middle Island (conventional maps, at the Crater; not to be confused with 5-parish point at Nevis Peak).
  • Uganda: Districts of Kyenjojo, Mbarara, Mubende and Sembabule (on most maps, and possibly other quadripoints more recent).
  • Vietnam: Provinces of Bac Can, Cao Bang, Ha Giang and Tuyen Quang (on most maps, with possible companions too).

Obviously in all such inconclusive cases, more research is needed, even if not always possible. (Countries not mentioned are believed on best available evidence not to have any quadripoints of their primary subdivisions.)

Void or dispute-pendant quadripoints

A pair of conflicting territorial claims can give rise to a void or dispute-pendant quadripoint: of the territory in dispute and the adjacent undisputed territories of the claimants with a fourth territory (or void area) claimed by neither of them. An international case of such a quadripoint on dry land can be inferred, if not actually found, in a remote area of the Nubian Desert involving both the Hala'ib Triangle and Bir Tawil (about midway between the River Nile and the Red Sea) where the long established but undemarcated international border along the 22nd parallel, as claimed by Egypt, is intersected by a similarly well established administrative boundary preferred and claimed by Sudan as the true international border.[46][47] A practically identical situation occurs on the boundaries of the Ilemi Triangle, where Sudan enjoys a second void quadripoint, in this case shared with Kenya. Another occurrence -- actually a chain of three such quadripoints linked to two separate unclaimed areas in a far busier location, indeed in coastal waters whose national sovereignty would otherwise have been zealously guarded -- is likewise inferrable where the southern end of the Alaska sector of the Canadian border aberrates into two crisscrossing versions or claim lines. These conflicting lines produce, besides two areas of overlapping claims, two small triangles of void or virtual high seas -- one having two pendant quadripoints and the other a third, all identifiable at fairly precise geocoordinates -- as they lurch through the narrows of Dixon Entrance toward their still indefinite boundary termination in the true high seas of the Pacific.[48][49]Yet another quadripoint of this type exists on the disputed Thai Cambodian boundary a short distance northeast of Preah Vihear temple. And finally, combining the only other two (of the seven) unclaimed or void areas on Earth, is a seventh dispute-pendant quadripoint, at the South Pole. Being at once a simple bilateral quadripoint and a far more complicated intersection of claim limits (an elevenfold 6-country point), the South Pole example combines two parcels of virgin unclaimed land with two parcels of Antarctic Treaty regulated territory (which have been variously claimed, disputed, recognized, ignored, disowned, reclaimed, etc., as national sovereign territory by Argentina, Australia, Chile, France, Great Britain and New Zealand, if not also Norway). But whatever the ultimate disposition of disputed national sovereignty, the intersection and quadripoint of two undisputedly pristine and two highly disputable territories endures.[50][51]The void areas meet the polar quadripoint between the 90th and 150th meridian west longitude (Marie Byrd Land) and, again, between the 20th meridian west and 45th meridian east (this latter sector, of indefinite extent, owing to the Norwegian exclusion of the South Pole from Queen Maud Land), while sovereign or treaty regulated areas converge at the polar quadripoint in the two intervals between the void areas.

See also

Notes and references

Notes
  1. ^ In common American English usage, the much more usual expression for the thing described by the term has been "four corners" (at least until the 1970s and perhaps even still). This is evidently because the most celebrated quadripoint in the world (which is located in the United States) is named "the Four Corners".
  2. ^ Although both the Nunavut Act and the Nunavut Land Claims Agreement state the intersection of 60°00'N latitude and 102°00'W longitude as the boundary between Manitoba, Saskatchewan, and the Northwest Territories, the actual, legal boundary point is marked by a survey monument boundary marker placed by the Manitoba Saskatchewan Boundary Commission in 1962.[25] According to Natural Resources Canada, Geodetic Survey Division, that monument's precise location is 59°59′57.98511″N 102°0′27.24027″W / 59.9994403083°N 102.0075667417°W / 59.9994403083; -102.0075667417 (NAD83), or about 400 metres (1,300 ft) west and slightly south of 60°N by 102°W.[26]
References
  1. ^ a b Akweenda, S. (1997). International Law and the Protection of Namibia's Territorial Integrity: Boundaries and Territorial Claims. Martinus Nijhoff. pp. 201–203. ISBN 9789041104120.
  2. ^ Nolan, J. (2003). "There are numerous points where three countries meet. Are there any with four?". Geographical. 75 (12): 19. ISSN 0016-741X. {{cite journal}}: Unknown parameter |month= ignored (help)
  3. ^ http://www.law.fsu.edu/library/collection/LimitsinSeas/IBS030.pdf
  4. ^ "Zambia". Encyclopædia Britannica (2010 Online Library Edition ed.). Encyclopædia Britannica. Retrieved 17 November 2010. {{cite encyclopedia}}: |edition= has extra text (help)
  5. ^ "The World Factbook 1990 Electronic Version". Central Intelligence Agency. 1993. Retrieved 17 November 2010.
  6. ^ at 238c: DB Warks., 3,4
  7. ^ http://books.google.com/books?id=oUmfAAAAMAAJ&q=%22four+shires+stone%22&dq=%22four+shires+stone%22&hl=en&ei=nOHdTM2TKsL58AbstZjaDw&sa=X&oi=book_result&ct=result&resnum=8&ved=0CEgQ6AEwBzgU
  8. ^ http://www.hunimex.com/warwick/four_shire_stone.html
  9. ^ Boundaries of the United States and the Several States, Franklin K. Van Zandt, 1976. pp. 22ff, 26f, 100-107.
  10. ^ http://alabamamaps.ua.edu/contemporarymaps/alabama/historical/index.html
  11. ^ http://www.mymississippigenealogy.com/ms-maps.html
  12. ^ http://www.moresnet.nl/english/geschiedenis_en.htm
  13. ^ Arnold, Guy (1997). The Resources of the Third World. Taylor & Francis. pp. 252, 319. ISBN 9781579580148.
  14. ^ Anderson, Ewan W. (2003). International Boundaries: A Geopolitical Atlas. Psychology Press. pp. 9, 116, 118. ISBN 9781579583750.
  15. ^ Hinz, Manfred O.; Gatter, Frank Thomas (2006). Global Responsibility – Local Agenda: The Legitimacy of Modern Self-Determination and African Traditional Authority. LIT Verlag Münster. p. 45. ISBN 9783825867829.
  16. ^ Griffiths, Ieuan Ll (1995). The African Inheritance. Psychology Press. p. 56. ISBN 9780415010924.
  17. ^ http://jungholz.enclaves.org/images/94.jpg and http://jungholz.enclaves.org/images/114.jpg with English translation in green here: http://jungholz.enclaves.org/
  18. ^ http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=de&tl=en&u=http%3A%2F%2Fwww.jungholz.tirol.gv.at%2Fsystem%2Fweb%2Fdefault.aspx (municipal website for 1342 date presently out of order)
  19. ^ http://ontology.buffalo.edu/smith/baarle/coochbehar.gif
  20. ^ Waiting for the Eskimo: An historical and documentary study of the Cooch Behar enclaves of India and Bangladesh (Research paper) by Brendan R Whyte. School of Anthropology, Geography and Environmental Studies, 2002, University of Melbourne, figure 5b on page 479 and figure 4b on page 473, respectively, both instances personally attested by author expert at http://article.gmane.org/gmane.culture.discuss.boundary-point/8342
  21. ^ http://ontology.buffalo.edu/smith/baarle.htm
  22. ^ http://ontology.buffalo.edu/smith/baarle/baarlemap.html quadripoint is shown just below and right of center of map above the word Rethse
  23. ^ "Nunavut Act". Department of Justice, Canada. Retrieved 28 October 2010.
  24. ^ "Nunavut Land Claims Agreement" (PDF). Nunavut Tunngavik Incorporated. Retrieved 28 October 2010.
  25. ^ "Manitoba - Northwest Territories - Nunavut - Saskatchewan Multi-point". The Corner Corner. Retrieved 29 July 2010.
  26. ^ Canadian Spatial Reference System Online Database, Natural Resources Canada, Geodetic Survey Division. GSD LONG Report for: "MON 157 (name), 674002 (unique number)" (online database requires free registration).
  27. ^ Boundaries of the United States and the Several States, Van Zandt, supra, p. 14, 21
  28. ^ http://historical-county.newberry.org/website/Montana/viewer.htm
  29. ^ mapserver.mytopo.com
  30. ^ http://atlas.nrcan.gc.ca/site/english/maps/historical/territorialevolution/
  31. ^ Maine Geological Survey
  32. ^ http://docs.unh.edu/ME/attn25nw.jpg
  33. ^ Private and Special Laws (of Maine) 1895, Chapter 123, dated March 5th, 1895, pursuant to Maine State Statutes (Secretary of State's Miscellaneous Papers, IV, p.53, dated April 12th, 1873
  34. ^ factfinder.census.gov
  35. ^ http://en.poehali.org/maps/100k--l34-074.html , downloadable map (English prompts available)
  36. ^ http://www.nuim.ie/staff/dpringle/igu_wpm/mladen.pdf
  37. ^ http://kart.statkart.no/adaptive2/default.aspx?gui=1&lang=2 (zoomable map)
  38. ^ http://www.skogsstyrelsen.se/episerver4/templates/skogensparlor.aspx (zoomable map)
  39. ^ http://www.baldwinsmaps.com/maps/610.jpg
  40. ^ http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=no&tl=en&u=http%3A%2F%2Fwww.adressa.no%2Fnyheter%2Farticle79264.ece
  41. ^ http://books.google.com/books?id=r4FJXXciuhsC&pg=PA286&lpg=PA286&dq=oman+saudi+yemen+trijunction&source=bl&ots=mQPI-5LWkL&sig=_Dng2V5mUA5R3bk7Y0mBqm8hG_U&hl=en&ei=cQboTMCLI4PGlQf1rt3ACQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBsQ6AEwAQ#v=onepage&q=oman%20saudi%20yemen%20trijunction&f=false , for tricountry point
  42. ^ http://www.mophp-ye.org/english/data.html , for official zip file of Yemeni governorate boundaries
  43. ^ "A real quadripoint?". blanchflower.org.
  44. ^ Hubbard, Bill, Jr. (2009). American Boundaries: the Nation, the States, the Rectangular Survey. University of Chicago Press. p. 164. ISBN 978-0-226-35591-7. Retrieved 14 November 2010.{{cite book}}: CS1 maint: multiple names: authors list (link)
  45. ^ "Four Corners PID AD9256" (text file). NGS Survey Monument Data Sheet. United States National Geodetic Survey. 7 May 2003. Retrieved 26 December 2006.
  46. ^ http://www.law.fsu.edu/library/collection/LimitsinSeas/IBS018.pdf
  47. ^ http://www.law.fsu.edu/library/collection/LimitsinSeas/maps/bs18.html
  48. ^ http://www.dur.ac.uk/resources/ibru/publications/full/bsb5-3_gray.pdf , figure 2, page 62
  49. ^ http://www.internationalboundarycommission.org/coordinates/PortlandCanal.htm
  50. ^ http://www.icsm.gov.au/mapping/images/antarctica.jpg
  51. ^ http://www.nsf.gov/od/opp/antarct/anttrty.jsp

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