2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/99299One of us quant-ph/0206077 (Nucl. Phys. B, 1970, 21, 321) has shown that for the particle with zero mass and spin s=1/2 there are three types of two-component equations (or one four-component equation with three different subsidiary conditions) which differ from one another by P, T and C properties. One of these equations is the two-component Weyl equation. In this note we give two other relativistic invariant equations.2 pagesQuantum PhysicsMathematical PhysicsExactly Solvable and Integrable Systemstext