PANDEY, R N; GIRISH, B H. Evaluation of some extractants for predicting soil sulphur availability to cowpea (Vigna unguiculata). The Indian Journal of Agricultural Sciences, Delhi, India, v. 76, n. 3, 2011. Disponível em: https://epubs.icar.org.in/index.php/IJAgS/article/view/2678. Acesso em: 20 oct. 2025.