by Amusia, M.Ya, Arifov, P.U., Baltenkov, A.S., Grinberg, A.A., Shapiro, S.G.
Published in Physics letters. A (01.01.1974)

by Arifov, P. U., Kalamazov, R. U., Shevelev, S. V., Lem, I. N., Paiziev, A. A., Li, F.
Published in Soviet Powder Metallurgy and Metal Ceramics (01.02.1988)