*[http://www.life.illinois.edu/ib/451/May%20(1988).pdf How Many Species are There on Earth?] Robert M. May
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*地球上有多少物种 [http://www.life.illinois.edu/ib/451/May%20(1988).pdf How Many Species are There on Earth?] Robert M. May, Science, New Series, Vol. 241, No. 4872. (Sep. 16, 1988), pp. 1441-1449.
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Science, New Series, Vol. 241, No. 4872. (Sep. 16, 1988), pp. 1441-1449.