“…Toute copie ou impression de ce fichier doit contenir la présente mention de copyright. [1,3,7,9,10,11,13,15,17] and the references given there. This is of interest in various aspects such as the Birch-Swinnerton-Dyer conjecture, the Siegel zero (see [7]) and the theory of modular forms of half-integral weight (see [16,18] [12].…”