WENDEL, J. G. Zero-Free Intervals of Semi-Stable Markov Processes. Mathematica Scandinavica, Berkeley, CA, United States, v. 14, p. 21–34, 1964. DOI: 10.7146/math.scand.a-10702. Disponível em: https://journals.msp.org/mscand/article/view/2602. Acesso em: 25 jul. 2026.