BUNDSCHUH, Peter; ZUDILIN, Wadim. Irrationality measures for certain $q$-mathematical constants. Mathematica Scandinavica, Berkeley, CA, United States, v. 101, n. 1, p. 104–122, 2007. DOI: 10.7146/math.scand.a-15034. Disponível em: https://journals.msp.org/mscand/article/view/663. Acesso em: 24 jul. 2026.