This was a six-volume series about the principal pilots, observers, etc. (PLM-winners) of WW I. Published in 1941, these are quite difficult to find. I have found one or two of them before, but never three of the six volumes. They are quite interesting and would be a welcome addition to a WW I aviation collection. Only ONE volume is left!
* Volume 3. Has a drawing of Heinrich Bongartz on the cover. Inside we find descriptions and drawings of Ernst Brandenburg, Julius Buckler, Hans-Joachim Buddecke, Franz Büchner, Walter von Bülow, Friedrich Christiansen, Carl Degelow, Albert Dossenbach, Eduard Ritter von Dostler, Hermann Fricke, Heinrich Gontermann, Robert Ritter von Griem, Wilhelm Griebsch, and Jürgen von Grone.