Types of quantum field thories
In particle physics the letters MSSM are an abbreviation for “minimally supersymmetric standard model”: an extension of the standard model of particle physics to a model (in particle phyiscs) with a minimum amount of extra global supersymmetry.
The original articles are
S. Dimopoulos and H. Georgi, Phys. Lett. B 117, 287 (1982).
Steven Weinberg, Phys. Rev. D 26, 287 (1982)