A Remark on the Level Sets of the Graph of Harmonic Functions Bounded by Two Circles in Parallel Planes. Journal of Partial Differential Equations, [S. l.], v. 28, n. 3, p. 197–207, 2015. DOI: 10.4208/jpde.v28.n3.1. Disponível em: https://www.global-sci.com/index.php/jpde/article/view/14954. Acesso em: 5 dec. 2025.