HELMY, A. M.; RAMADAN, M. F. Agronomic performance and chemical response of sunflower (Helianthus annuus L.) to some organic nitrogen sources and conventional nitrogen fertilizers under sandy soil conditions. Grasas y Aceites, [S. l.], v. 60, n. 1, p. 55–67, 2009. DOI: 10.3989/gya.032508. Disponível em: https://grasasyaceites.revistas.csic.es/index.php/grasasyaceites/article/view/546. Acesso em: 8 feb. 2023.