1. D. N. Kursanov and P. A. Solodkov,Zh. Obshch. Khim., 1935,5, 1487 [Russ. J. Gen. Chem., 1935,5 (Engl. Transl.)].
2. V. I. Savin,Zh. Org. Khim., 1978,14, 2090 [Russ. J. Org. Chem., 1978,14 (Engl. Transl.)].
3. A. Alberoda, Gonzalez Nogal, and A. Maria Pedrosa R.,An. Quim., 1978,74 (7–8), 1108.
4. A. Alberoda, Gonzalez Nogal, and A. Maria Pedrosa R.,An. Quim., 1978,74 (7–8), 1104.
5. A. L. Buchachenko and A. M. Vasserrosa,Stabil'nye radikaly [Stable Radicals], Khimiya, Moscow, 1973, 165 pp. (in Russian).