1. Snyder, John P., "Map Projections--A Working Manual", U.S. Geological Survey
    Professional Paper 1395 (Supersedes USGS Bulletin 1532),
    United State Government Printing Office, Washington D.C., 1987.
2. Snyder, John P. and Voxland, Philip M., "An Album of Map Projections",
    U.S. Geological Survey Professional Paper 1453 ,
    United State Government Printing Office, Washington D.C., 1989.
3. "Cartographic Projection Procedures for the UNIX Environment-
    A User's Manual" by Gerald I. Evenden,
    USGS Open File Report 90-284and Release 4 Interim Reports (2003)
4. Snyder, John P., "Flattening the Earth -
    Two Thousand Years of Map Projections", Univ. Chicago Press, 1993
5. Wolfram Mathworld "Gnomonic Projection"
    http://mathworld.wolfram.com/GnomonicProjection.html
    Accessed: 12th November 2009
6. "New Equal-Area Map Projections for Noncircular Regions", John P. Snyder,
    The American Cartographer, Vol 15, No. 4, October 1988, pp. 341-355.
7. Snyder, John P., "Map Projections--A Working Manual", U.S. Geological
    Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
    State Government Printing Office, Washington D.C., 1987.
8. "Software Documentation for GCTP General Cartographic Transformation
    Package", U.S. Geological Survey National Mapping Division, May 1982.
9. Department of Land and Survey Technical Circular 1973/32
    http://www.linz.govt.nz/docs/miscellaneous/nz-map-definition.pdf
10. OSG Technical Report 4.1
    http://www.linz.govt.nz/docs/miscellaneous/nzmg.pdf
11. Formules et constantes pour le Calcul pour la
    projection cylindrique conforme à axe oblique et pour la transformation entre
    des systèmes de référence.
    http://www.swisstopo.admin.ch/internet/swisstopo/fr/home/topics/survey/sys/refsys/switzerland.parsysrelated1.31216.downloadList.77004.DownloadFile.tmp/swissprojectionfr.pdf