1. USA Patent No. 3222299 (1965).
2. Japanese Patent No. 48-43883 (1973).
3. L. P. Gostintseva et al., in: Synthetic Fibres [in Russian] (edited by A. B. Pakshver), Khimiya, Moscow (1969).
4. M. S. Zakhar'evskii, Kinetics and Catalysis [in Russian], LGU, Leningrad (1963).
5. E. M. Fettes (editor), High Polymers, Vol. 19, The Chemical Reactions of Polymers, Wiley-Interscience, New York (1964) [Russian translation: Mir, Moscow (1967)].