1. W. Reppe and E. Keyssner, German Patent 618,120 (1935);
2. N. Sawa, S. Okamura, M. Yasuda, and Y. Hosokawa, Japanese Patent 74/09467 (1974)
3. Poly-N-vinylcarbazole. I. Preparation of N-vinyl-carbazole
4. S. R. Sandler, U.S. Patent 3,679,700 (1972).