Sanchez Institut de F isica d'Altes Energies, p.8193 ,
The People's Republic of China ,
Zerwas Laboratoire de l'Acc el erateur Lin eaire, 91405. ,
Universit a d i T rieste e INFN Sezione di Trieste ,
8 Supported by the National Science Foundation of China. 9 Supported by the Danish Natural Science Research Council. 10 Supported by the UK Particle Physics and Astronomy Research Council. 11 Supported by the US Department of Energy, grant DE-FG0295-ER40896. 12 Also at CERN, 1211 Geneva 23,Switzerland. 13 Supported by the US Department of Energy, contract DE-FG05-92ER40742. 14 Supported by the US Department of Energy, contract DE-FC05-85ER250000. 15 Permanent address, 08208 Barcelona, Spain. 16 Supported by the Bundesministerium f ur Bildung, Wissenschaft, Forschung und Technologie, Fed. Rep. of Germany. 17 Supported by the Direction des Sciences de la Mati ere, C.E.A. 18 Supported by F onds zur F orderung der wissenschaftlichen Forschung, Austria. 19 Supported by the US Department of Energy, grant DE-FG03-92ER40689. 20 Now a t S c hool of Operations Research and Industrial Engireering.S.A. 21 Now a t S c h w eizerischer Bankverein, pp.14853-3801 ,
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DOI : 10.1016/0168-9002(92)90794-5