KORHONEN, R.; TOHGE, K.; ZHANG, Y.; ZHENG, J. A lemma on the difference quotients. Annales Fennici Mathematici, [S. l.], v. 45, n. 1, p. 479–491, 2020. DOI: 10.5186/aasfm.2020.4521. Disponível em: https://afm.journal.fi/article/view/135866. Acesso em: 8 sep. 2024.