The Stereoviews of Carleton Watkins
http://www.carletonwatkins.org/
The Bancroft Library Pictorial Collection, University of California, Berkeley, CA
http://bancroft.berkeley.edu/collections/pictorial.html#photo
Bruce Hathaway, “About Carleton Watkins”, Smithsonian Magazine
http://www.smithsonianmag.com/people-places/carleton-watkins.html
Yosemite History: Carleton E. Watkins
http://www.yosemite.ca.us/library/watkins/
Carleton Watkins at Fraenkel Gallery, San Francisco, CA
http://www.fraenkelgallery.com/
Carleton E. Watkins, Three Brothers, 4480 ft., Yosemite, ca. 1865–1866. Albumen print. Courtesy Fraenkel Gallery, San Francisco, USA.