1. B. M. Barbashov and V. V. Nesterenko,Introduction to Relativistic String Theory [in Russian], Énergoatomizdat, Moscow (1987); English transl., World Scientific, Singapore (1990).
2. B. M. Barbashov, V. V. Nesterenko and A. M. Chervyakov,Theor. Math. Phys.,40, 572 (1979).
3. G. P. Pron'ko, A. V. Razumov and L. D. Solov'ev,Sov. J. Part. Nucl.,14, 229 (1983).
4. S. P. Novikov,Sov. Math. Dokl.,24, 222 (1981).
5. E. Witten,Commun. Math. Phys.,92, 455 (1984).