AMBER force field parameters were taken form 
http://amber.scripps.edu/dbase.html

Citation from those site:
"As has always been the case, the parameter information in the above file is 
in the public domain, and may be redistributed or used in other programs. 
Any such use should include proper citations, and any modifications 
to the parameters should be prominently noted."


Article:

W.D. Cornell, P. Cieplak, C.I. Bayly, I.R. Gould, K.M. Merz, Jr., 
D.M. Ferguson, D.C. Spellmeyer, T. Fox, J.W. Caldwell and P.A. Kollman. 
A second generation force field for the simulation of proteins, 
nucleic acids, and organic molecules. 
J. Am. Chem. Soc. 117, 5179-5197 (1995).

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OPLS force field parameters from the article:
J. Am. Chem. Soc. 1988 v.110. pp.1657-1666


