BUNDSCHUH, Peter. Irrationalität und Transzendenz gewisser Reihen. Mathematica Scandinavica, Berkeley, CA, United States, v. 28, p. 226–232, 1971. DOI: 10.7146/math.scand.a-11019. Disponível em: https://journals.msp.org/mscand/article/view/2278. Acesso em: 25 jul. 2026.