1. “Federal Radionavigation Plan-Volume 3, Radionavigation System Characteristics DOD-4650.4-P-III, DOT-TSC-RSPA-81-12-III March, 1982
2. “Federal Radionavigation Plan-Volume 2, Requirements DOD-4650.4-P-I, DOT-TSC-RSPA-81-12-1 March, 1982
3. Ruedger , W. H. Feasibility of Collision Warning, Precision Approach and Landing Using the GPS Research Triangle Institute, NASA CR 165675 March, 1981