Characterisation of pyrogenic carbon humic acids by solid state NMR - Novotny, Etelvino Henrique; Hayes, M. H. B.; Azevêdo, Eduardo Ribeiro de; Benites, V. M.; Madari, Beata Emoke; Cunha, T. J. F.; Bonagamba, Tito José (Symposium on NMR Spectroscopy in Soil and Geo Sciences, 2006)