1. G. I. Kudryavtsev and A. M. Shchetinin, in: Thermally-resistant, Heat-resistant, and Incombustible Fibers [in Russian], A. A. Konkin, editor, Khimiya, Moscow (1978).
2. Information from the VNIIV, Khim. Volokna, No. 3, (1975) (tabular contribution).