After reading A Company of Tanks I wondered whether it would be worth having a list of links to editions of WWI books that are out of print or otherwise unobtainable and legally available as either a pdf download, text/HTML version, or other format. As a starter the AWM has C.E.W. Bean's "Official History of Australia in the War of 19141918" available as seperate pdf volumes and Project Gutenburg has W.H.L. Watson's "Adventures of a Despatch-Rider" as either a text download with no images or HTML with images.