Solutions of relativistic radial quasipotential equations

A systematic approach to the investigation of relativistic radial quasipotential equations is developed. Solutions are obtained with zero-value boundary condition at the point $r=0$ and also Jest solutions of the equation
$$ [2c\sqrt{{q^2}+{m^2c^2}}-H^{\mathrm{rad}}_{0}-V(r;E_q)]\psi_l(q,r)=0 $$
on the half-axis $[0,\infty)$ for the $S$-wave ease $(l=0)$ when $H^{\mathrm{rad}}_0=2mc^{2}\ch\biggl(\frac{i\hbar}{mc}\frac{d}{dr}\biggr)$.