1. R. J. Graut , in The Chemistry of Amidines and Imidates, ed. Patai, S., Wiley, New York, 1975, ch. 6(and references cited therein).
2. G. Häfelinger , in The Chemistry of Amidines and Imidates, ed. Patai, S., Wiley, New York, 1975, ch. 1.
3. G. Fodor , and B. A.Philips, in The Chemistry of Amidines and Imidates, ed. Patai, S., Wiley, New York, 1975, ch. 2.
4. Conformational isomerism of the amide group - a review of the IR and NMR spectroscopic evidence
5. Substituent Effect on the N–H Stretching Absorptions of 2-(Substituted anilino)pyridines