第一篇：
The Natural Selection Model of Conceptual Evolution
Robert J. Richards
Philosophy of Science, Vol. 44, No. 3 (Sep., 1977), pp. 494-501
(article consists of 8 pages)

第二篇：
Comment on "The Natural Selection Model of Conceptual Evolution"
Donald T. Campbell
Philosophy of Science, Vol. 44, No. 3 (Sep., 1977), pp. 502-507
(article consists of 6 pages)