Humus composition of mountain soils in Central Japan with special reference to the distribution of P type humic acidKyoichi Kumada, Shinobu Ohta, Yasuo Ohsumi et al.|Soil Science & Plant Nutrition|1967Cited by 184
The chemical nature of the green fraction of P type humic acidOsamu Sato, Kyoichi Kumada|Soil Science & Plant Nutrition|1967Cited by 47