1. For a review see e.g: (a) Meislich H.“Pyridine and its Derivatives”Klingsberg E. Interscience New York 1962 Vol. III 509
2. Synthetic and Natural Sources of the Pyridine Ring
3. Joule, J. A. and Smith, G. F. 1986.“Heterocyclic Chemistry”,, 2nd Ed., 157England: Van Nostrand Reinhold Co, Workingham.