1. I. N. Bernshtein, I. M. Gel'fand, and S. I. Gel'fand, Usp. Mat. Nauk,28, No. 3, 3?29 (1973).
2. P. Deligne, J. S. Milne, A. Ogus, and Kuang-yen Shih, Hodge Cycles, Motives, and Shimura Varieties, Lecture Note in Math., 900, Springer, Berlin (1982).
3. R. P. Langlands, "Problems in the theory of automorphic forms," in: Lectures in Modern Analysis and Applications, III. Lecture Notes in Math., Vol. 170, Springer, Berlin (1970), pp. 18?61.
4. A. Pressley and G. Segal, Loop Groups, Clarendon Press, Oxford, University Press, New York (1986).