GRIGOR'EV, Yu. A. Some inequalities for gradients of harmonic functions. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 49, n. 8, p. 1135–1136, 1997. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5106. Acesso em: 5 dec. 2025.