[1] DEUTSCHE ELEKTRON SYNCHROTRON, HAMBURG, WEST GERMANY
[2] UNIV HAMBURG, EXPTL PHYS INST 2, HAMBURG, WEST GERMANY
[3] UNIV HEIDELBERG, INST HOCHENERGIEPHYS, HEIDELBERG, WEST GERMANY
[4] UNIV BONN, INST PHYS, BONN, WEST GERMANY
[5] MAX PLANCK INST, PHYS & ASTROPHYS, MUNICH, WEST GERMANY
[6] TH AACHEN, PHYS INST 3, LEHESTUHL B, AACHEN, WEST GERMANY