The best-known form of liberation theology is that which developed within the Catholic Church in Latin America in the 1960s, arising principally as a moral reaction to the poverty and social injustice in the region, which is the most unequal in the world. The term was coined in 1971 by the Peruvian priest Gustavo Gutiérrez, who wrote one of the movement's defining books, "A Theology of Liberation". Other noted exponents include Leonardo Boff of Brazil, and Jesuits Jon Sobrino of El Salvador and Juan Luis Segundo of Uruguay.