1. W. Carruthers, J. Chem. Soc., 4186 (1953).
2. B. D. Tilak, Proc. Indian Acad. Sci., 33, Sect. A, 71 (1951).
3. T. N. Sidorenko, G. A. Terent'eva, V. S. Raida, O. S. Andrienko, Yu. V. Savinykh, and V. S. Aksenov, Khim. Geterotsikl. Soedin., No. 12, 1618 (1982).
4. J. W. Emsley, J. Feeney, and L. H. Sutcliffe, High-Resolution NMR Spectroscopy, Pergamon, Oxford (1966).
5. I. Heilbron and H. M. Brunbury (editors), Dictionary of Organic Compounds, Vol. 3, Eyre and Spottiswoode, London (1953).