1. Illustrierte Flora von Mittel-Europa, J. F. Lehmanns Verlag, München, 1925, V(1), 526–530.
2. Commission E of the German Federal Public Health Department, Monograph “Hyperici herba, Johanniskraut”, 1984, correction 1989.
3. Thesis, University of Bonn, in preparation; results presented at the DPhG-Doktorandentagung at Kloster Banz/Staffelstein, 1995.