Medvedeva, S. M.; Plaksina, M. E.; Shikhaliev, K. S. The Synthesis of 6-R-2,2,4-Trimethyl-1,2-Dihydroquinoline- and 6-R-4-R’-2,2,4-Trimethyl-1,2,3,4-Tetrahydroquinoline-8-Carboxylic Acids – the Structural Analogues of Helquinoline. J. Org. Pharm. Chem. 2015, 13, 21-25.