The study of livestock farming systems in a research framwork : proceedings of the second International Symposium on Livestock Farming Systems, Saragossa, Spain, September 11-12, 1992 / Gibon, Annick Flamant, Jean Claude Livestock Agriculture 656 PUD 1994 A051 Or. Wageningen, Netherlands : PUDOC, 1994 1994 Text 449 p. : EAAP publication ;