9GERASIMAWICZ W V,BYLER D M.Carbon-13 CPMAS NMR and FITRspectroscopic studies of humic acid[J].Soil Science,1985,139(2):270-278.
10PIOTROWSKI E G,VALETINE K M.Solid-state,C-13,crosspolarization,'magic-angle' spinning,NMR spectroscopy studies of sewage sludge[J].Soil Science,1984,137(5):194-203.