1. [I] Doll, R.E.; Gunderson, E.K.E. Hobby Interest and Leisure Activity Behaviour among Station Members in Antarctica. Unit Report No. 69–34, US Navy Medical Neuropsychiatric Research Unit, San Diego, California (1969).
2. Eberhard, J.W. The Problem of Off-Duty Time in Long-Duration Space Missions. NASA CR 96721, three volumes, Serendipity Associates, McLean, Virginia (1967).
3. Sostaric, R.R. Powered Descent Trajectory Guidance and Some Considerations for Human Lunar Landing. AAS Guidance and Control Conference, Breckenridge, Colorado, February 3–7, 2007.