Ren, Zhongjiao; Cao, Weiguo; Tong, Weiqi; Chen, Jie; Wang, Changqing
Journal of Heterocyclic Chemistry, 2008 , vol. 45, # 1 p. 85 - 90

Saito; Kambe; Nakano; et al.
Synthesis, 1983 , vol. No. 3, p. 210 - 212