1. Alford RA, Dixon PM, Pechmann JHK (2001) Global amphibian population declines. Nature 414:449–500
2. Allison P (2004) Convergence problems in logistic regression. In: Altman M, Gill J, McDonald PM (eds) Numerical issues in statistical computing for the social scientist. John Wiley & Sons Inc, Hoboken
3. Amphibian Research and Monitoring Initiative. (2007). ARMI national atlas for amphibian distributions, Anura. 2007. United States Geological Survey, Patuxent Wildlife Research Center, Laurel, Maryland
http://www.pwrc.usgs.gov/armiatlas/order.cfm?recordID=Anura
(accessed August 28, 2007)
4. Babbitt KJ, Baber MJ, Tarr TL (2003) Patterns of larval amphibian distribution along a wetland hydroperiod gradient. Canadian Journal of Zoology 81:1539–1552
5. Bluemle JP (2000) The face of North Dakota. 3rd edition. Dakota Geological Survey Educational, Series 26, Bismarck