2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/94696The enveloping algebra,$D_{n}$,of fermions is extended on the lattice to include the discrete space invariance.This extended algebra,denoted X, has the space symmetry as a factor : $X/D_{n}$ = space group.Mathematical Physicsrfj1867text