Some properties of the solutions of a quasipotential equation

A study is made of the order of the energy levels of bound two-particle systems described by relativistic equations that can be transformed to a local form. It is found that the energy levels of the quasi-potential equation are normally ordered if the quasipotential is a nonincreasing function of the energy. A method is proposed for numerical solution of the quasipotential equation with the relativistic kinematics taken into account explicitly and the relativistic dynamics taken into account by perturbation theory.