by Dennett-Thorpe, J., de Bruyn, A. G.
Published in Nature (London) (03.01.2002)

by Laing, R. A.
Published in Nature (London) (14.01.1988)

by Norris, R. P., Kesteven, M. J., Allen, David A., Troupe, E.
Published in Monthly notices of the Royal Astronomical Society (01.09.1988)

by Allington-Smith, J. R., Lilly, S. J., Longair, M. S.
Published in Monthly notices of the Royal Astronomical Society (01.03.1985)