1. NASA: Plant and animal life safely recovered from biosatellite II. NASA News Release 67-239 (1967).
2. Young, R. S.: Weightlessness and the developing frog egg. Preprint COSPAR, July 24?29. London 1967.
3. Briegleb, W.: Ein Modell zur Schwerelosigkeits-Simulation an Mikroorganismen. Naturwissenschaften54, 167 (1967).
4. Briegleb, W.: Is there a common geotropic dependency in organisms? Preprint XVIII th I. A. F. Congress, Sept. 24?30, Belgrade 1967.
5. Levine, R. B.: Zero gravity simulation, in:Benedikt, E. T.: Weightlessness ? physical phenomena and biological effects. New York: Plenum Press 1961.