  The energy spectrum of high energy cosmic rays emitted by sources change
during propagation in the Galaxy. Using the spectrum observed at the Earth and
two different transport models, based on anomalous and normal diffusion
equations, we have retrieved an average value of the cosmic ray injection
exponent at Galactic sources taking into account the inhomogeneity of the
interstellar medium. We have shown that the average value of the injection
index $p$, obtained in the framework of both transport models, equals to $p\sim
(2.8-3.0)$.
