Long time lurker. First time poster. I second the previous posting about Patrick Agte's book: Michael Wittmann and the Tiger Commanders of the Leibstandarte. Costly, but worth it. Simpson's book, however, is an expensive doorstop--worst history book I have ever bought. As previously mentioned, the Villers Bocage: Through the Lens is a great book--about $40. Although Barkmann is not listed, Panzer Aces and Panzer Aces 2 contains a 50-100 page discussion of German tank commanders. PA contains Generalmajor Dr. Franz Bake, Hermann Bix, Rudolf von Ribbentrop, Hans Bolter (of Paw of the Tiger fame in Squad Leader--my favorite scenario), Michael Wittmann and Albert Ernst. PA 2 contains Sepp Brandner, Fritz Fessmann, Kurt Knispel, Johannes Kummel, Karl Nicolussi-Leck and Hermann von Oppeln-Bronikowski. PA and PA 2 are written by Franz Kurowski. They are available at www.jjfpub.mb.ca along with a ton of other armor books.