For the prevention of unjust enrichment of a defendant the courts make available a number of restitutionary remedies to a plaintiff. These remedies developed separately, and they differ somewhat in their characteristics, but during recent years writers have seen that there is a single principle underlying them all, whether they are administered at law or in equity.
John W. Wade,
Restitution -- 1962 Tennessee Survey,
16 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol16/iss3/25