Darwin Unbuttoned
Charles Darwin's Notebooks, 1836–1844: Geology, Transmutation of Species, Metaphysical Enquiries
transcribed and edited by Paul H. Barrett and Peter J. Gautrey and Sandra Herbert and David Kohn and Sydney Smith
The Correspondence of Charles Darwin Volume 3: 1844–1846
edited by Frederick Burkhardt, edited by Sydney Smith
April 28, 1988 issue
