1. 1931. Report of the R101 Inquiry. H.M.S.O. Cmd. 3825
2. Appel, W. D. and Worner, R. K. 1931. Nat. Adv. Cttee for Aeronautics, Tech. Rep. No. 393, Sept.
3. McNicholas, H. J. and Hedrick, A. F. 1930. Nat. Adv. Cttee for Aeronautics, Tech. Rep. No. 335, March