Detail of: Unknown. Untitled (self portrait and mirror). 1930s. Gelatin silver print, 2 in. × 2 1/8 in. (5.1 × 5.4 cm). Saint Louis Art Museum. https://www.slam.org/collection/objects/62704/.
Below are a few reference titles that can be found at the Hatfield Library. These materials would be a good place to start for research.
The Self Portrait
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American Faces
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Frida Kahlo
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The Self-Portrait
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Eye to I: Self Portraits from 1900 to Today
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Wikipedia is a great resource for getting general info about something, but because anyone can contribute or change its content, it is sometimes considered unreliable. It is a good place to start your research, but it is best to double check what you find against other sources.