1. J. Biel, E. J. Bleser, D. Duke, T. Ferbel, D. Freytag, B. Gobbi, L. Kenah, J. Rosen, R. Ruchti, P. Slattery andD. Underwood:Phys. Rev. Lett.,36, 504, 507 (1976);Phys. Lett.,65 B, 291 (1976);J. Biel: University of Rochester Thesis, unpublished (1977).
2. A. Babaev, E. Brachman, G. Eliseev, A. Ermilov, Yu. Galaktionov, Yu. Gorodkov, Yu. Kamishkov, E. Leikin, V. Lubimov, L. Ponomdrev, V. Shevchenko, V. Tinnchik, O. Zeldovich, V. Böhmer, J. Engler, N. Flanger, H. Keim, F. MÔnnig, K. Pock andH. Schopper: CERN Report (June 23, 1976, submitted toNucl. Phys., B).
3. H. de Kerret, E. Nagy, M. Regler, W. Schmidt-Parzefall, K. R. Schubert, K. Winter, A. Brandt, H. Dibon, G. Flügge, F. Niebergall, P. E. Schumacher, J. J. Aubert, C. Broll, G. Coignet, J. Favier, L. Massonnet, M. Vivargent, W. Bartl, H. Eichinger, Ch. Gottfried andG. Neuhofer:Phys. Lett.,63 B, 477, 483 (1976).
4. S. D. Drell andK. Hiida:Phys. Rev. Lett.,7, 199 (1961);R. T. Deck:Phys. Rev. Lett.,13, 169 (1964).
5. For a review seeE. L. Berger: Argonne Report ANL/HEP 7506, Daresbury Study Weekend Series No. 8, edited byJ. B. Dainton andA. J. G. Hey.