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-I and A-5 ofthe American Society of Agronomy; and Divisions C-2 and C-3 of the Crop Science Society of America, Chicago, Illinois, 2 December 1985. - Aviad, Tsila (American Society of Agronomy, Inc., 1990)