1. Peskin, M. E. and Schroeder, D. V., An Introduction to Quantum Field Theory. Addison-Wesley, Reading, MA 1995
2. Wilson, K., Phys. Rev 179 (1969) 1499
3. Isgur, N. and Wise, M. B., in B Decays (ed. Stone, S. ). World Scientific, Singapore 1994
4. Bigi, I. I., Khoze, V. A., Uraltsev, N. G. and Sanda, A. I., in CP violation (ed. Jarlskog, C. ). World Scientific, Singapore 1989
5. Buras, A. J. and Harlander, M. K., in Heavy Flavors (ed. Buras, A. J. and Lindner, M. ). World Scientific, Singapore 1992