Dictionnaire des racines scientifiques / André Cailleux et J. Komorn
Elsevier´s telecommunications dictionary : in six languages / compilado e organizado por ordem alfabética inglesa por W. E. Clason
Postmarks of South West Africa Under South African Administration : A comprehensive study 1914 - 1977 Including a complete listing of all S.W.A. Post Offices with a special sections on S. African military campaign postmarks 1914-1915 railways sations cacellations 1915 - 1977 telegraph Stations, airmail history of S.W.A. cencor cachets, ships postmarks, etc. / Ralph F. Putzel
Illustraded encyclopedia of stamp collecting / Otto Hornung; fotografias de Zdenek Humpál