[1] UNIV BARI, DIPARTIMENTO FIS, I-70121 BARI, ITALY
[2] UNIV BARI, IST NAZL FIS NUCL, I-70121 BARI, ITALY
[3] UNIV FLORENCE, DIPARTIMENTO FIS, I-50121 FLORENCE, ITALY
[4] UNIV FLORENCE, IST NAZL FIS NUCL, I-50121 FLORENCE, ITALY
[5] IST NAZL FIS NUCL, LAB NAZL FRASCATI, I-00044 FRASCATI, ITALY
[6] UNIV PERUGIA, DIPARTIMENTO FIS, I-06100 PERUGIA, ITALY
[7] UNIV PERUGIA, IST NAZL FIS NUCL, I-06100 PERUGIA, ITALY
[8] UNIV ROMA TOR VERGATA, DIPARTIMENTO FIS, I-00173 ROME, ITALY
[9] UNIV ROMA TOR VERGATA, IST NAZL FIS NUCL, I-00173 ROME, ITALY
[10] NASA, GODDARD SPACE FLIGHT CTR, GREENBELT, MD 20771 USA
[11] NEW MEXICO STATE UNIV, LAS CRUCES, NM 88003 USA
[12] UNIV SIEGEN, D-5900 SIEGEN, GERMANY
[13] TATA INST FUNDAMENTAL RES, BOMBAY 400005, MAHARASHTRA, INDIA