CALLEJA, E., SANCHEZ-GARCIA, M.A., BASAK, D., SANCHEZ, F.J., CALLE, F., YOUINOU, P., MUNOZ, E., SERRANO, J.J., BLANCO, J.M., VILLAR, C., LAINE, T., OILA, J., SAARINEN, K., HAUTOJARVI, P., MOLLOY, C.H., SOMERFORD, D.J. and HARRISON, I., 1998. Physical Review B. 58, 1550-