). Determinants of human immunodeficiency virus type 1 escape from the primary CD8+ cytotoxic Y lymphocyte response. J Exp Math 200: 1243-1256. 36. Matsen E, MA Nowak (2004). Win-stay, lose-shift in language learning from peers. P Natl Acad Sci USA 101: 18053-18057. 37. Michor F, Y Iwasa, MA Nowak (2004