SZULKIN, Andrzej. An example concerning the topological character of the zero-set of a harmonic function. Mathematica Scandinavica, Berkeley, CA, United States, v. 43, p. 60–62, 1978. DOI: 10.7146/math.scand.a-11763. Disponível em: https://journals.msp.org/mscand/article/view/1881. Acesso em: 25 jul. 2026.