1. U.S. Patents 2,453,088; 2,753,595; 2,607,072; 3,006,029; 3,239,882; 3,239,883; 3,486,193; 3,486,194; 2,970,341; 2,496,625; 2,765,491.
2. U.S. Patent 3,271,819 (Sept. 13, 1966).
3. and ?Engineering Principles of Plasticating Extrusion,? Van Nostrand Reinhold, New York (1970).
4. and U.S. Patent 3,411,179 (Nov. 19, 1968).