YU, K.-W.; KULKARNI, M.-N. On the order and the lower order of differential polynomials. Tamkang Journal of Mathematics, [S. l.], v. 42, n. 4, p. 475–482, 2011. DOI: 10.5556/j.tkjm.42.2011.647. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/647. Acesso em: 8 may. 2024.