If the work was received privately from the artist rather than being publicly posted, or that it is different from version publicly posted by the artist (such as having higher resolution, lack of censorship, watermark, etc.), then the source may be left blank, left as the filename, or description of where the commission was delivered. Non-web source tag may be applicable if the artist have not posted that version of the work online.
If the work was posted to another site by the commissioner, use second-party source instead.
If the artist provided the uploader with the file but the work was not a commission, use artist-provided artwork instead.
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