1. Conrad H.R., Klopfenstein. (1988) In:Alfalfa and Alfalfa Improvement(Hanson A.A., Barnes D.K., Hill R.R. Jr., eds.), American Society of Agronomy Monograph29.
2. Rumbaugh M.D., Caddel J.L., Rowe D.E. (1988) In:Alfalfa and Alfalfa Improvement(Hanson A.A., Barnes D.K., Hill R.R. Jr., eds.) American Society of Agronomy Monograph29.
3. Smith D.L. (1988) In:Alfalfa and Alfalfa Improvement(Hanson A.A., Barnes D.K., Hill R.R. Jr., eds.), American Society of Agronomy Monograph29.
4. McCoy T.J., Bingham E.T. (1988) In:Alfalfa and Alfalfa Improvement(Hanson A.A., Barnes D.K., Hill R.R. Jr., eds.), American Society of Agronomy Monograph29.
5. Aamodt O.S. (1941)In: Climate and Man, Yearbook Agr. (USAD) US Government Printing Office, Washington, 439–458.