During World War II, this guide to identifying warplanes was given by Richfield Oil distributors and dealers to their customers with the proviso: 'In making this book available to the public, the Richfield Oil Corporation of New York has revealed no information which would be of aid to the enemies of our country. All items included in the contents have been compiled from established, trustworthy sources and constitute general information designed to aid the layman in identifying friendly and hostile aircraft.' [Facsimile Reprint]