2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35650In gravitation theory, a fermion field must be regarded only in a pair with a certain tetrad gravitational field. These pairs can be represented by sections of the composite spinor bundle $S\to\Si\to X^4$ where values of gravitational fields play the role of parameter coordinates, besides the familiar world coordinates.10 pp LaTeX file. The report on the Workshop "New Frontiers of Gravitation Theory" (Monteroduni, August 1995)General Relativity and Quantum Cosmologytext