Humic substances in soil and crop sciences: Selected readings : Proceedings of a symposium cosponsored by the International Humic Substances Society; divisions S-3, S-2, S-4, S-5, and S-7 of the Soil Science Society of America; divisions A-1 and A-5 of the American Society of Agronomy; and divisions C-2 and C-3 of the Crop Science Society of America, Chicago, Illinois, 2 December 1985 - MacCarthy, Patrick. (American Society of Agronomy, Inc.;Soil Science Society of America, Inc., 1990)