1. Greenhill, L.J., Booth, R.S., Ellingsen, S.P., et al.: 2003, ApJ 590, 162.
2. Herrnstein, J.R., Moran, J.M., Greenhill, L.J., et al.: 1999, Nature 400, 539.
3. Herrnstein, J.R., Moran, J.M., Greenhill, L.J. and Trotter A.S., 2004, in preparation.
4. Humphreys, E.M.L., Argon, A.L., Greenhill, L.J., Reid, M.J. and Moran, J.M.: 2003, in Romney (eds.), VLBA 10th Anniversary Proceedings.
5. Liljeström, T. and Gwinn, C.R.: 2002, IAU 206, 55, eds. Migenes, Reid.