  A realistic axiomatic formulation of nonrelativistic quantum mechanics for a
single microsystem with spin is presented, from which the most important
theorems of the theory can be deduced. In comparison with previous
formulations, the formal aspect has been improved by the use of certain
mathematical theories, such as the theory of equipped spaces, and group theory.
The standard formalism is naturally obtained from the latter, starting from a
central primitive concept: the Galilei group.
