1. Ger. Pat., 3 402 734 A1 (1984) to G. Frank and G. Neubauer (BASF AG.).
2. Fr. Pat. 1 483 300 (1967) K. Adam and E. Haarer (BASF AG.).
3. Organic Functional Group Hydrogenation
4. Jpn. Pat., 7 106 885 to S. Taira and A. Kuroda (Toray Industries, Inc.).