Hugh Morgan. Soviet Aces of World War 2 . , Reed International Books Ltd , 1997.

This Red Air Force propaganda poster dates from 1937/38, and fea-tures the 1-16. The Polikarpov fighter was christened the 'Rata' ('Rat') by the Nationalist Air Force in Spain during that country's civil war, and the description stuck and was duly adopted by the Lufwaffe in World War 2 (via Seibel)