1. For reviews, see A. Mueller, Physics Repts. 73, 237 (1981);
2. G. Altarelli, Physics Repts. 81, 1 (1982).
3. E. Feinberg and I. Ya. Pomeranchuk, Nuovo Cimento Suppl. 3, Ser. 10, 652 (1956).
4. See J. D. Bjorken, Proceedings of the 1979 SLAC Summer Institute on Particle Physics, ed. A. Mosher, for some details of the apparatus. There may be some problems, not considered there, with regard to spontaneous pair creation by the strong electromagnetic fields. I thank J. Hamilton for some stimulating conversations on practicalities.
5. K. Konishi, A. Ukawa, and G. Veneziano, Nucl. Phys. B157, 45 (1979);