Documentaries still play an important part in Dutch film industry. The International Documentary Film Festival Amsterdam, held annually in November, is considered one of the largest documentary film festivals in the world. Famous documentary directors pre- and postdating the unofficial Documentary School include Joris Ivens, Johan van der Keuken and Jos de Putter. Ivens won a César Award and a Golden Lion, as well as a career achievement award at the Venice Film Festival. Jos de Putter is now head of the Documentary film department of the VPRO, one of the main Dutch public television stations.