Dr. Karl Thomas GmbH
Patent: US4886814 A1, 1989 ;

Combes
Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences, 1890 , vol. 111, p. 422

Ema, Tadashi; Sugiyama, Yasushi; Fukumoto, Minoru; Moriya, Hiroyuki; Cui, Jing-Nan; Sakai, Takashi; Utaka, Masanori
Journal of Organic Chemistry, 1998 , vol. 63, # 15 p. 4996 - 5000