1. Batchelor, R.A., McCulloch, M.G., Whiteoak, J.B. (1981), M.N.R.A.S. 194, 911.
2. Booth, R.S., Delgado, G., Hagström, M., Johansson, L.E.B., Murphy, D.C., Olberg, M., Whyborn, N.D., Greve, A., Hansson, B., Lindström, C.O., Rydberg, A. (1989), Astron. Astrophys. 216, 315.
3. Booth, R.S., Johansson, L.E.B. (1990), these proceedings.
4. Caswell, J.L., Haynes, R.F. (1981), M.N.R.A.S. 194, 33P.
5. Cohen, R.S., Dame, T.M., Garay, G., Montani, J., Rubio, M., Thaddeus, P. (1988), Astrophys. J. 331, L95.