TRALLI, G. Some Zaremba-Hopf-Oleinik Boundary Comparison Principles at Characteristic Points. Bruno Pini Mathematical Analysis Seminar, [S. l.], v. 6, n. 1, p. 54–68, 2015. DOI: 10.6092/issn.2240-2829/5890. Disponível em: https://mathematicalanalysis.unibo.it/article/view/5890. Acesso em: 2 may. 2024.