  The dilation invariance is studied in the framework of Epstein-Glaser
approach to renormalization theory. Some analogues of the Callan-Symanzik
equations are found and they are applied to the scalar field theory and to
Yang-Mills models. We find the interesting result that, if all the fields of
the theory have zero masses, then from purely cohomological consideration, one
can obtain the anomalous terms of logarithmic type.
