Fokker D.21 Research & Bibliography

G.H. Kamphuis, #63: The Fokker D.XXI (Profile Publications/1967)
Dated but some good info

J. Vasco & P. Cornwell, Zestorer: the Messerschmitt 110 and its Units in 1940 (JAC Publications/1995)
Background on actions of April/May 1940

Jerry Campbell, Messerschmitt Bf 110 Zestorer in Action (Squadron/Signal Publications/1977)
Background on actions of April/May 1940

Warren Eberspacher, Monograph #1: Fokker D-XXI, Dutch and Danish Service (Phalanx Publishing/1994)
The best source on the D21 by far.

W. Green & G. Swanborough, The Complete Book of Fighters (Salamander Books/1994-2001)
A good general resource.

Janusz Ledwoch, Fokker D-XXI (Wydawnictwo Militaria/1995)
Polish text, but good source of photos (with english captions!)

Beknopte Geschiedenis van de Koninklijkeluchtmacht (A Brief History of the Royal Netherlands Air Force) Personnel Department, Dutch Air Force (via Johan "Viper" Lemmers)