1. R. E. Neitzel, R. Hirschkron and R. P. Johnston, General Electric co. "Study of Turbofan Engines Designed for Low Energy Consumption". Prepared for NASA under NAS3-19201, not issued.
2. R. Hirschkron, R. P. Johnston and R. E. Neitzel, General Electric Co., Lynn, Mass. "Study of unconventional Aircraft Engines Designed for Low Energy Consumption". Prepared for NASA under NAS3-19519, not issued.