1. For a review, see S.J. Brodsky, G. McCartor, H.-C. Pauli, S.S. Pinsky, Part. World. 3 (1993) 109. S.J. Brodsky, H.-C. Pauli, S.S. Pinsky, hep-ph/9705477.
2. C.M. Bender, S.S. Pinsky, B. van de Sande, Phys. Rev. D48 (1993) 816. S.S. Pinsky, B. van de Sande, Phys. Rev. D49 (1994) 2001. S.S. Pinsky, B. van de Sande, J.R. Hiller, Phys. Rev. D51 (1995) 726.