  Reciprocal transformations mix the role of the dependent and independent
variables to achieve simpler versions or even linearized versions of nonlinear
PDEs. These transformations help in the identification of a plethora of PDEs
available in the Physics and Mathematics literature. Two different equations,
although seemingly unrelated, happen to be equivalent versions of a same
equation after a reciprocal transformation. In this way, the big number of
integrable equations could be greatly diminished by establishing a method to
discern which equations are disguised versions of a common underlying problem.
Then, a question arises: Is there a way to identify different versions of an
underlying common nonlinear problem? Other useful applications of reciprocal
transformations are subsequently discussed and illustrated with examples.
