  In this work we compile a few differential equations (ODEs) that arise from
the relativistic equations in cosmological models that consider the
``constants'' as scalars functions dependent on time and they are described as
perfect as well as viscous fluids. The general idea of the paper is to show how
to solve the equations of the models through dimensional techniques
(self-similarity). The results are compared with those obtained by other
authors and new solutions are introduced.
