2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90285In previous papers quant-ph/0206077, quant-ph/0206078, quant-ph/0206079 we have shown that there exist three types of the relativistic equations for the massless particles. Here we show that for the free particles and antiparticles with the mass m>0 and the arbitrary spin $s \geq 1/2$ there also exist three types of nonequivalent equations.3 pagesQuantum PhysicsMathematical PhysicsExactly Solvable and Integrable Systemstext