1. Cenker M, Trenton and Baxter G E 1961 US 3005820
2. Su W Y and Knifton J F 1988 US 4788289
3. Subrahmanyam, M, Kulkarni S J and Rao A V R 1995 Indian J. Chem. Technol. 2 237
4. Seetharamanjaneya S P, Raghavan K V, Rao P K and Kulkarni S J 2002 US 143180 A1
5. Forni L, Stern G and Gatti M 1987 Appl. Catal. 29 161