BRUN, Viggo; KNUDSEN, Finn F. On the Possibility of Finding Certain Criteria for the Irrationality of a Number Defined as a Limit of a Sequence of Rational Numbers. Mathematica Scandinavica, Berkeley, CA, United States, v. 31, p. 231–236, 1972. DOI: 10.7146/math.scand.a-11429. Disponível em: https://journals.msp.org/mscand/article/view/2216. Acesso em: 25 jul. 2026.