K. Reiner, P. Grabmayr, G. Mauser, G. Mertens, G.J. Wagner, J. Friedrich, N. Voegler, K.T. Knöpfle, J. Ryckebusch, K. Heyde, D. Van Neck, M. Waroquier Physics Letters B 228 (1), 31-361989A1Published while none of the authors were employed at the CMMDOI http://dx.doi.org/10.1016/0370-2693(89)90520-0