Lacroix, Magali, et al. The American Journal of Clinical Nutrition, 2006: 84(5): 1070-1079.
Kinda old, but: Demling, Robert H., and DeSanti, Leslie. Annals of Nutrition and Metabolism, 2000: 44:21-29.
And I think somewhere on the Internets Alan Aragon recommended a protein blend as well (well, whole foods and blends).