  The objectives of this article are three-fold. Firstly, we present for the
first time explicit constructions of an infinite family of \textit{unbalanced}
Ramanujan bigraphs. Secondly, we revisit some of the known methods for
constructing Ramanujan graphs and discuss the computational work required in
actually implementing the various construction methods. The third goal of this
article is to address the following question: can we construct a bipartite
Ramanujan graph with specified degrees, but with the restriction that the edge
set of this graph must be distinct from a given set of "prohibited" edges? We
provide an affirmative answer in many cases, as long as the set of prohibited
edges is not too large.
