Panzer Tracts is the final word in technical Panzer reference. These softcover books tell the story of German World War armour and its development in words, photos and highly accurate 1:35 scale drawings from Hilary L. Doyle.
The first three volumes reprinted are 4-3 Pz.Kpfw.IV Ausf.H and J, 8-1 Sturmpanzer and 16-1 Bergepanther and can be ordered directly from Panzerwrecks site here.