Reputation allows evolution of cooperation by indirect reciprocity. This arrangement is commonly called reciprocity or mutual recognition. This sits at the apex of an interplay between sovereignty, comity, consent, and reciprocity. Vampire bats also demonstrate a sense of reciprocity and altruism. Euler also conjectured the law of quadratic reciprocity. There are several different ways to express reciprocity laws. Reciprocity, Generalized Exchange, and Productive Exchange. Disapproval is often enough to make people comply with norm of reciprocity. California does not have license reciprocity with other states. The primary aspects of mutualism are free association, reciprocity and gradualism, or dual power. Mouqol is the Baklunish god of Trade, Negotiation, Ventures, Appraisal, and Reciprocity. Gift giving corresponded with the expectation of reciprocity. Trivers argues that friendship and various social emotions evolved in order to manage reciprocity. This is a consequence of the reciprocity theorem of electromagnetics. In 1911, another controversy arose regarding Laurier's support of trade reciprocity with the United States.