1. A. M. Popov, Anilinokrasochnaya Promyshlennost',3, 391 (1933).
2. A. A. Balandin and A. N. Titova, Uch. Zapiski MGU,2, 229 (1934).
3. C. F. Winans, J. Amer. Chem. Soc.,61, 3564 (1939).
4. Tsutomu Sasa, J. Soc. Organ. Synt. Chem.,12, 183 (1954).
5. Kiyoshi Hoizumi and Tatsuo Yamanaka, Kagaku Kénkyudzë Khokoku,32, 164 (1956).