  We construct effective Hamiltonians which despite their apparently
nonrelativistic form incorporate relativistic effects by involving parameters
which depend on the relevant momentum. For some potentials the corresponding
energy eigenvalues may be determined analytically. Applied to two-particle
bound states, it turns out that in this way a nonrelativistic treatment may
indeed be able to simulate relativistic effects. Within the framework of hadron
spectroscopy, this lucky circumstance may be an explanation for the sometimes
extremely good predictions of nonrelativistic potential models even in
relativistic regions.
