SZULKIN, A. An example concerning the topological character of the zero-set of a harmonic function. MATHEMATICA SCANDINAVICA, [S. l.], v. 43, p. 60–62, 1978. DOI: 10.7146/math.scand.a-11763. Disponível em: https://www.mscand.dk/article/view/11763. Acesso em: 28 apr. 2024.