Huxley, T.H. (April 1860). ART. VIII. – Darwin on the origin of Species. Westminster Review. 541 – 70. Посетен на 2008-06-19. „What if the orbit of Darwinism should be a little too circular?“
Huxley, T.H. (April 1860). ART. VIII. – Darwin on the origin of Species. Westminster Review. 541 – 70. Посетен на 19 юни 2008. „What if the orbit of Darwinism should be a little too circular?“