A great introduction to the Diemer–Duhm Gambit is now available: 10-page article by Bob Jensen. It concentrates on two critical variations:
- 5...c5 6.d5 exd5 7.cxd5 exf3 8.Nxf3 Bd6 (Keres).
- 5...Bb4 (Kmoch).
Especially 6.fxe4 is an interesting improvement idea to the Kmoch variation: