Barth remained at Bergen from 1961 to 1972. During this time his own work developed in two key ways. First, he developed research projects inside Norway (and published a study entitled "The Role of the Entrepreneur in Social Change in Northern Norway" in 1963). Second, he began writing more purely theoretical works that secured his international reputation within anthropology. These included "Models of Social Organization" (1966) and especially the small, edited volume, "Ethnic Groups and Boundaries: The Social Organization of Cultural Difference" (1969). Barth's introduction to "Ethnic Groups and Boundaries" became his most well-known essay and "ended up among the top 100 on the social science citation index for a number of years.".