The World's Helicopters
Putnam World Aeronautical Library
Series produced in the mid-1970s to provide an overview history of selected aviation topics, each being illustrated with photographs throughout. Eight varied subjects were covered in the series (search using the subtitle for other volumes).
The Domain of the Helicopter
Seventh Louis Bleriot Memorial Lecture (10th March, 1954)
Study of the helicopter as given for the Louis Bleriot Memorial Lecture in 1954. Typescript with diagrams and photographs to the rear.