1. E. B. Merkushev, Synthesis, 923 (1975).
2. S. Stavber, M. Jereb, and M. Zupan, Synthesis, 1487 (2008).
3. C. Hansch, A. Leo, and R. W. Taft, Chem. Rev., 91, 165 (1991).
4. P. Imming, P. Klaperski, M. T. Stubbs, G. Seitz, and D. Gundisch, Eur. J. Med. Chem., 36, 375 (2001).
5. B. T. O’Neill, “Pyridone-fused azabicyclic- or cytisine derivatives, their preparation and their use in addiction therapy,” Int. Publ. No. WO 98/18798 A1, Priority date Oct. 30, 1996, Publ. May 7, 1998.