  In recent years, many papers have been devoted to the regularity of doubly
nonlinear singular evolution equations. Many of the proofs are unnecessarily
complicated, rely on superfluous assumptions or follow an inappropriate
approximation procedure. This makes the theory unclear and quite chaotic to a
nonspecialist. The aim of this paper is to fix all the misprints, to follow
correct procedures, to exhibit, possibly, the shortest and most elegant proofs
and to give a complete and self-contained overview of the theory.
