1. Müller TE, Hultzsch KC, Yus M, Foubelo F, Tada M (2008) Chem Rev 108:3795–3892
2. Carter AB, Harris N, Kippax JW, Rathmell C, Reason AJ, Scarlett J, Sharif M, Turner K (1986) EP0223814A1, 18 Dec 1986
3. Baer M (1949) US Patent 2,492,086, 20 Dec 1949
4. Rehberg CE, Dietz TJ, Meiss PE, Dixon MB (1952) Ind Eng Chem 44:2191–2195
5. Kurek G, Pedain J, Halpaap R, Sonntag M (1998) US patent 5,821,326, 13 Oct 1998