1. D.P. Barber, K. Heinemann, G. Ripken: in this issue of Z. Phys. C.; see also DESY 91-047 by the same authors
2. A.W. Chao: Nucl. Instrum. Methods 180 (1981) 29, also in: Physics of High Energy Particle Accelerators, American Institute of Physics Proceedings 87, p. 395, 1982
3. K. Yokoya: DESY Report 86-57, 1986
4. Y.S. Derbenev: University of Michigan, Ann Arbor Preprint. UM HE 90-23, 1990; Y.S. Derbenev: University of Michigan, Ann Arbor Preprint, UM HE 90-30, 1990; Y.S. Derbenev: University of Michigan, Ann Arbor Preprint, UM HE 90-32, 1990
5. Y.S. Derbenev, A.M. Kondratenko: Sov. Phys. JETP 37 (6) (1973) 968