@article{Williams, author = {Williams, R. M.}, title = {Propositions on Intergroup Hostility and Conflict}, series = {L. Wilson and W.L. Kolb (Eds.), Sociological Analysis. An Introductory Text and Case Book, New York (Harcourt, Brace and Co.) 1949, pp. 740-761.}, journal = {L. Wilson and W.L. Kolb (Eds.), Sociological Analysis. An Introductory Text and Case Book, New York (Harcourt, Brace and Co.) 1949, pp. 740-761.}, language = {en} } @book{NesseWilliams, author = {Nesse, R. M. and Williams, G. C.}, title = {Evolution and Healing. The New Science of Darwinian Medicine. London (Phoenix) 1994.}, language = {en} }