1. On Type-L multivariable linear systems;Sandell;Automatica,1973
2. Digital controllers for VTOL aircraft;Stengel,1976
3. The design of digital-adaptive controllers for VTOL aircraft;Stengel;NASA CR-144912,1976
4. A spiral guidance approach concept for commercial VTOL Operations;Hoffman;NASA CR-132651,1975
5. Design principles for digital autopilot synthesis;Berman;J. Aircraft,1974