  We study zeros distribution for meromorphic functions of the form
$\sum\limits_n \dfrac{c_n}{(z-t_n)^2}$, where $\sum\limits_n
\dfrac{|c_n|}{|t_n|^2} <\infty$. We prove an analog of the classical Keldysh
theorem and discuss a relation between zero-free functions of this form and
second order differential equtions with polynomial coefficients.
