by Storchak, V.G., Kirillov, B.F., Pirogov, A.V., Duginov, V.A., Grebinnik, V.G., Mamedov, T.N., Ol'shevsky, V.G., Xhukov, V.A., Brewer, J.H., Morris, G.D.
Published in Physics letters. A (21.12.1992)