WANBY, Göran. Subharmonic and Strongly Subharmonic Functions in Case of Variable Coefficients. Mathematica Scandinavica, Berkeley, CA, United States, v. 22, p. 283–309, 1968. DOI: 10.7146/math.scand.a-10892. Disponível em: https://journals.msp.org/mscand/article/view/2410. Acesso em: 25 jul. 2026.