1. F. Bourdin, M. Costantini, M. Jouffret, G. Lartigau, US Patent 3,849,502, to Rhone Poulenc, SA.
2. S. Herman, S. Bloch III, US Patent 3,580,956, to Universal Oil Products Company.
3. S. Umemura, N. Takamitsu, T. Hamamoto, N. Kuroda, US Patent 4,078,006, to UBE Industries.
4. M. Costantini, D. Laucher, J.-M. Popa, FR 2,693,457, to Rhone Poulenc Chimie.
5. Solid Acids for Green Chemistry