 According to Lenin biographer David Shub, writing in 1965, it was Lenin's ideas and example that "constitutes the basis of the Communist movement today".Socialist states following Lenin's ideas appeared in various parts of the world during the 20th century.Writing in 1972, the historian Marcel Liebman stated that "there is hardly any insurrectionary movement today, from Latin America to Angola, that does not lay claim to the heritage of Leninism".