Interpretations of current copyright law, specifically the "fair use" clause, indicates that materials taken from the Web may be used freely as long as it is not for commercial use and if proper credit is given. We have used images from the Web in good faith, since we are using such for educational purposes and since we acknowledge all sources.  

An drawing is the legal intellectual propert of the artist. Legally, written permission to use that drawing must be granted by the artist.