LEHTO, O. On an extension of the concept of deficiency in the theory of meromorphic functions. MATHEMATICA SCANDINAVICA, [S. l.], v. 1, p. 207–212, 1953. DOI: 10.7146/math.scand.a-10378. Disponível em: https://www.mscand.dk/article/view/10378. Acesso em: 9 may. 2024.