How should images that are included in the classroom or in material be referenced?
The most advisable way is to cite the source and name of the author on each image. If this cannot be done, they must be identified suitably, and a section must be created with the credits of the images used (eg an additional page or at the foot of each of the pages containing images).
There are various ways of citing an image or photograph: APA style, MLA, etc. For more information, "How to cite a photograph" can be consulted in WikiHow.