1. U. S. Pat. 2,589,198; 2,589,201 (1952).
2. U. S. Pat. 2,407,895 (1946).
3. USSR Author's Certificate 193,652; Byul. Izobret., No. 7 (1967).
4. U. S. Pat. 2,426,175 (1947).
5. Yu. S. Smirnov, A. A. Petrov, and A. F. Simin'kova, in: New Developments in the Gathering and Pretreatment of Crude in Oil Fields [in Russian], VNIIOÉNG, Moscow (1968).