In 1950, his studies were interrupted when he and writer Jan Trefulka were expelled from the Communist Party for "anti-party activities." Trefulka described the incident in his novella "Pršelo jim štěstí" ("Happiness Rained on Them", 1962). Kundera also used the expulsion as an inspiration for the main theme of his novel "Žert" ("The Joke", 1967). After Kundera graduated in 1952, the Film Faculty appointed him a lecturer in world literature. In 1956 Kundera was readmitted to the Party but was expelled for the second time in 1970. Along with other reformist communist writers such as Pavel Kohout, he was peripherally involved in the 1968 Prague Spring. This brief period of reformist activities was crushed by the Soviet invasion of Czechoslovakia in August 1968. Kundera remained committed to reforming Czechoslovak communism, and argued vehemently in print with fellow Czech writer Václav Havel, saying, essentially, that everyone should remain calm and that "nobody is being locked up for his opinions yet," and "the significance of the Prague Autumn may ultimately be greater than that of the Prague Spring." Finally, however, Kundera relinquished his reformist dreams and moved to France in 1975. He taught for a few years in the University of Rennes. He was stripped of Czechoslovak citizenship in 1979; he has been a French citizen since 1981.