Before revision:  In 2019 Mastrolilli ]  initiated a systematic study of IMPs arising from Constraint Satisfaction Problems (CSP) of the form CSP(\Gamma), that is, CSPs in which the type of constraints is limited to relations from a set \Gamma.
After revision:  In 2019 Mastrolilli SODA'19] initiated a systematic study of IMPs arising from Constraint Satisfaction Problems (CSP) of the form CSP(\Gamma), that is, CSPs in which the type of constraints is limited to relations from a set \Gamma.