Rao, V. Rajeshwar; Rao, T. V. Padmanabha
Indian Journal of Chemistry, Section B: Organic Chemistry Including Medicinal Chemistry, 1985 , vol. 24, p. 979 - 981

Mueller, Uwe; Timpe, Hans-Joachim; Kuestermann, Ekkehardt; Urban, Klaus
Zeitschrift fuer Chemie (Stuttgart, Germany), 1981 , vol. 21, # 6 p. 224