1. Barbier, H. (1931). French Patent 710,295. (1932a). Helv. Chim. Acta 15, 592. (1932b). U.S. Patent 1,892,128.
2. Barbier, H. (1934). U.S. Patent 1,951,123. (1936). Helv. Chim. Acta 19, 1345.
3. Baur, A. (1888). German Patent 47,599. (1891a). German Patent 62,362. (1891b). Ber. Dtsch. Chem. Ges., 24, 2836, 2841.
4. Baur, A. (1892). German Patent 62,632. (1894). German Patent 87,130.