1. Analytical Manufacturing Control in the Nitrogen Industry [in Russian], Khimiya, Moscow (1968), Issue No. 16.
2. F. G. Dyatlovitskaya and É. D. Maktaz, Khim. Volokna, No. 6, 69?70 (1968).
3. Z. Ghersin, Revista de Chimie,18, No. 2, 112?113 (1967).
4. G. Reinisch and W. Jaeger, Khimiya i Tekhnol. Polimerov, No. 12, 10?18 (1962).
5. F. M. Shemyakin and E. N. Zelenina, Zh. Anal. Khim.,23, No. 9, 1376?1379 (1968)