1. Über Kondensationen der Aldehyde mit Ammonik zu Pyridinbasen
2. A.J.M. Barheigen, and C.H. Gehshuberts, Japanese Patent (unexamined) 55-43100 (1980) (to Stamicarbon Corp.
3. T. Kawahito, K. Koga, and M. Kuniyoshi, Japanese Patent (unexamined) 52-31075 (1977) (to Ube Co.
4. C.D. Chang and W.H. Lang, US Patent No.4 220 783 (1980) (to Mobil Oil Corp.).