I am writing my thesis and came across an image on Wikipedia that I would like to use. The licensing on this image is:
I, the copyright holder of this work, release this work into the public domain. This applies worldwide. In some countries this may not be legally possible; if so: I grant anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.
Should I still include a reference to indicate this image is not my own work, if so, who should be given credit (the author is not known in this case)?