Source Book of Vertical Take-Off Aircraft Jolly Green Giants; US Combat Helicopters Helicopter, An Illustrated History Helicopters Hubschraubermuseum Bückeburg Air Navigation R.A.F. Militaire Kentekens Helicopters of the world Helicopters of the world Helicopters of the world Geschiedenis van de Luchtvaart in Nederland kasteel van Breda en de Koninklijke Militaire academie 1928-1958