 These instances of cooperation are regimes.The most commonly cited definition of regimes comes from Stephen Krasner, who defines regimes as "principles, norms, rules, and decision-making procedures around which actor expectations converge in a given issue-area".Not all approaches to regime theory, however, are liberal or neoliberal; some realist scholars like Joseph Grieco have developed hybrid theories which take a realist based approach to this fundamentally liberal theory.