ドレイクの方程式 - Wikipedia
^ Drake, F.D., Discussion of Space Science Board, National Academy of Scientific Conference on Extraterrestorial Intelligent Life, November 1961, Green Bank, West Virginia.
^ Wallenhorst, S. G. "The Drake Equation Reexamined," ROYAL ASTRON. SOC. QUARTERLY JOURNAL vol.22, P. 380, 1981. PDF
^ Milan M....
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