“…Applications of Clifford algebras methods in general relativity appeared also, e.g., in [35,90,54,55,57,58,62,103,104,105,119,134,154], and suggest new ways for looking to the gravitational field. Clifford algebras methods, have been applied successfully also in quantum field theory, as , e.g., in [60,138] and more recently in string and p-brane theories, with noticeable results ( [25]- [34], [136,137]) which are worth to be more carefully investigated.…”