To do this, we must often email or contact the copyright holders and ask them to allow us to use it under the Creative Commons Attribution-Sharealike 3.0 Unported License (CC-BY-SA) or a CC-BY-SA-compatible license and, if possible, also the GNU Free Documentation License (GFDL) (unversioned, with no invariant sections, front-cover texts, or back-cover texts). See for more.
This means that a contributor's work might appear in print or digital versions of this encyclopedia that are sold in stores. It might appear in books, or other specialized subsets of the full text—teacher curriculum packets, publicity brochures, other uses we haven't thought of yet. It will certainly be used by other websites that legally copy our content.
About half the people we ask say yes, especially if it's explained that the license terms mean it is more widely appreciated and that we do not want to use all their material, but just one image or item. See for more.
This page explains what must be done if you want to use content that's copyrighted, whether you know who produced it or you don't.
It sometimes happens that users post text from other websites claiming to have permission to do so. Sometimes, images from other websites are uploaded and claimed to be under a free license (CC-BY-SA, GFDL, public domain, {{}}, or others.) If the external website does not have any indication that such claims are well-founded, it is a good idea to try to verify such claims.
If you yourself have found an image or text source and want to contact the photographer or copyright holder up-front to secure permission before uploading the image or adding the text, you should also follow these guidelines.
You may also choose to explain that the author does not give up any of their rights to use the text: they are still free to publish the text elsewhere or to license the same text to other parties under any other license.
For images, you are not limited to CC-BY-SA: any free license will do. If the photographer's identity is unclear (for instance, if an image was uploaded stating the photographer's name and claiming a free license, but the image cannot be found on the web), ask them to confirm that the image is theirs. In any case, ask them to confirm the claimed license. For CC-BY-SA, point out the points mentioned above. Any free license must allow all of the following, for both the image itself as well as any modified versions based on it: