On the Location of Zeros of Solutions of $f'' + A(z)f = 0$ where $A(z)$ is Entire.

Wu, S. (1994). On the Location of Zeros of Solutions of $f’’ + A(z)f = 0$ where $A(z)$ is Entire. MATHEMATICA SCANDINAVICA, 74, 293–312. https://doi.org/10.7146/math.scand.a-12498