Babson, R. W. (1950). Chapter XXXV – Playing with Gravity, Actions and Reactions [Second Revised Edition]. New York: Harper & Brothers Publishers [1]Archived 2007-09-27 at the Wayback Machine Page over to Chapter XXXV for Roger W. Babson's description of the Gravity Research Foundation.
Babson, R. W. (1950). Chapter XXXV – Playing with Gravity, Actions and Reactions [Second Revised Edition]. New York: Harper & Brothers Publishers [1]Archived 2007-09-27 at the Wayback Machine Page over to Chapter XXXV for Roger W. Babson's description of the Gravity Research Foundation.