2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/52561The quantum algebra of observables of the massive closed bosonic string in 1+3 dimensions has been developed so far in the rest frame of the string. In this paper a method to write this algebra in a manifestly Lorentz covariant form is explained and compared with an alternative approach in the literature.11 PagesHigh Energy Physics - Theorytext