Kreutzkamp,N.; Mengel,W.
Chemische Berichte, 1967 , vol. 100, # 3 p. 709 - 714

Patel, Dinesh V.; Schmidt, Robert J.; Biller, Scott A.; Gordon, Eric M.; Robinson, Simon S.; Manne, Veeraswamy
Journal of Medicinal Chemistry, 1995 , vol. 38, # 15 p. 2906 - 2921

Bentley, Robert L.; Dingwall, John G.
Synthesis, 1985 , # 5 p. 552 - 553