Neptune, A., M. Tabatabai, e J. Hanway. 1974. Sulfur Fractions and Carbon-Nitrogen-Phosphorus-Sulfur Relationships in Some Brazilian and Iowa Soils . Anais Da Escola Superior De Agricultura Luiz De Queiroz 31 (janeiro), 605-19. https://doi.org/10.1590/S0071-12761974000100047.