CHIANG, Y. -m.; LAINE, I.; WANG, S. Oscillation Results for Some Linear Differential Equations. Mathematica Scandinavica, Berkeley, CA, United States, v. 77, p. 209–224, 1995. DOI: 10.7146/math.scand.a-12562. Disponível em: https://journals.msp.org/mscand/article/view/1111. Acesso em: 25 jul. 2026.