1. W. Wendelin undA. Harler, Mh. Chem.105, 563 (1974).
2. W. Wendelin, A. Harler undA. Fuchsgruber, Mh. Chem.107, 141 (1976).
3. W. Wendelin undA. Harler, Mh. Chem.107, 133 (1976).
4. W. Wendelin undA. Fuchsgruber, Mh. Chem.105, 755 (1974).
5. E. Knoevenagel undR. Werner, Justus Liebigs Ann. Chem.281, 25 (1894).