UMAR, N. .; REHMAN, H. . Crop Productivity Variations in U.P.: A Regional Analysis. National Geographical Journal of India , [S. l.], v. 57, n. 2, p. 55–64, 2022. Disponível em: https://www.ngji.in/index.php/ngji/article/view/544. Acesso em: 20 jun. 2025.