Images must be cited like all other resources. If you use an image you did not create, you must provide a citation. Images should be cited in all cases, even if the image is very small, or in the public domain. The citation should be accessible in the context of the image's use (within a Powerpoint presentation, on a web page, in a paper, etc.).
Image citations should include the following information at a minimum:
It is also useful to include date, culture, and rights information, if known.
Citations can be formatted according to the citation style you are using.
Nadar [Gaspard Félix Tournachon], Felix Nadar in the Gondola of a Balloon, ca. 1863, J. Paul Getty Museum
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