See also: V.T. Dolgopolov, W. Hansen, A.A. Shashkin, E.V. Devyatov, A.V. Aristov, D. Schmerek, J.P. Kotthaus
PACS: 72.20.My, 73.40.Kp, 72.70.+m, 73.40.Hm, 73.50.Td