Desmond, Adrian J. (September 13, 2002). "Charles Darwin". Encyclopædia Britannica. Archived from the original on February 6, 2018. Retrieved February 11, 2018.
Desmond, Adrian J. (September 13, 2002). "Charles Darwin". Encyclopædia Britannica. Archived from the original on February 6, 2018. Retrieved February 11, 2018.