User blog comment:P進大好きbot/Images without Copyright/@comment-3427444-20200131171829/@comment-24061664-20200131234743

I think that pictures expressing mathematical equations should not be deleted just because there is no copyright tag. Copyright is intended to protect the original expression of an idea in the form of a creative work, and I do not think mathematical equations are not protected by copyright. For those images of comics or photos, we could delete them if there are no copyright notice. Just note that the pictures of Sushi Kokuuhen was uploaded by the author, Doom Kobayashi himself in Japanese Gwiki and therefore it is OK.