  Robin Forman's highly influential 2002 paper titled A User's Guide to Discrete Morse Theory presents an overview of the subject in a very readable manner. As a proof of concept, the author determines the topology (homotopy type) of the abstract simplicial complex of disconnected graphs of order $n$ (which was previously done by Victor Vassiliev using classical topological methods) using discrete Morse theoretic techniques, which are purely combinatorial in nature. The techniques involve the construction (and verification) of a discrete gradient vector field on the complex. However, the verification part relies on a claim that doesn't seem to hold. In this note, we provide a couple of counterexamples against this specific claim and also an alternative proof of the claim that the constructed discrete vector field is indeed a gradient vector field. 
A note on an application of discrete Morse theoretic techniques on the   complex of disconnected graphs