Power for the Pioneers, the Green & E.N.V. Aero Engines by A.E. Tagg. This softcover 76 page book contains photos and drawings of the various versions of these engines. Also, many small photos of all the pre WWI aircraft that utilized these powerplants. As this book was published in 1990, you will need to source it from the secondary market such as bookfinder.com Nice reference book if you do not have to pay an excessive amount.