1. Azc�rate, I.N., Cersosimo, J.C. and Colomb, F.R.: 1986,Rev. Mex. Astron. Astrof. 13, 15.
2. Azc�rate, I.N., Cersosimo, J.C. and Colomb, F.R.: 1987a,Rev. Mex. Astron. Astrof. 15, 3.
3. Azc�rate, I.N., Cersosimo, J.C. and Colomb, F.R.: 1987b,RetRev. Mex. Astron. Astrof. 15, 125.
4. Burton, W.B.: 1988, in: G.L. Verschuur and K.I. Kellermann (eds.),Galactic and Extragalactic Radio Astronomy, Second Edition, Springer-Verlag.
5. Cersosimo, J.C.: 1990,Astrophys. J. 349, 67.