1. Becker, R. H. & Helfand, D. J. Nature 313, 115–118 (1984).
2. Weiler, K. W. & Pangia, N. Astr. Astrophys. 90, 269–282 (1980).
3. Reynolds, S. & Chevalier, R. Preprint (National Radio Astronomy Observatory, 1984).
4. Becker, R. H. & Helfand, D. J. Astrophys. J. 283, 154–157 (1984).
5. Helfand, D. J. & Becker, R. H. Proc. Conf. Crab-like SNR USA (in the press).