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The existence of pure-strategy Nash equilibrium in games with payoffs that are not quasiconcave
Baye, Michael R., (1990)
Characterizations of the existence of equilibria in games with discontinuous and non-quasiconcave payoffs
Baye, Michael R., (1993)
Quasi-Variational Inequalities without Concavity Assumptions
Tian, Guoqiang, (1991)