Waag veel, riskeer niets! : G.A. Koppen (1890-1970) en de vlucht van de Postduif Vliegende dienders : De politie in de lucht Barnstormers & Speed kings road to Kitty Hawk soviet air force Women Aloft International Encyclopedia of Aviation War in the air : aerial wonders of our time Black wings : the American black in aviation Flying machines : the picture of the men, women and machines which first conquered space Air forces of the world : an illustrated directory of all the world's military air powers Aircraft aircraft