German and Austrian Aviation of World War I by Hugh W. Cowin

I love how the book is illustrated with detailed and vibrant artwork.

X Planes : Research Aircraft 1891-1970: A Unique Pictorial Record of Flying Prot

X Planes : Research Aircraft 1891-1970: A Unique Pictorial Record of Flying Prototypes, their Designers and Pilots (Osprey Aviation Pioneers 1). Title : X Planes : Research Aircraft 1891-1970: A Unique Pictorial Record of Flying Prototypes, their Designers and Pilots (Osprey Aviation Pioneers 1).