Translations:Water reverberations/17/en

${\begin{aligned}={\varepsilon }_{3}Z^{3}\left[{1}+\left(-{\varepsilon }_{0}{\varepsilon }_{3}\right)Z^{3}+{\left(-{\varepsilon }_{0}{\varepsilon }_{3}\right)}^{2}Z^{6}+\dots \right]={\frac {{\varepsilon }_{3}Z^{3}}{{1}+{\varepsilon }_{0}{\varepsilon }_{3}Z^{3}}}.\end{aligned}}$

(20)