1. Abies, H.D. 1971, Publ.U.S.Naval Obs., Series II, Vol. 20, Part 4.
2. Ball, R., Sargent, A.I., Scoville, N.Z., Lo, K.Y., and Scott, S.L. 1985, Ap.J.(Letters), 298, L21.
3. Bieging, J.H., Blitz, L., Lada, C.J., and Stark, A.A. 1981, Ap.J., 247, 443.
4. Bloemen, J.B.G.M., Caraveo, P.A., Mermsen, W., Lebrun, F., Maddalena, R.J., Strong, A.W., and Thaddeus, P.T. 1984, Astron.Ap., 193, 37.
5. Boulanger, F., Bystedt, J., Casoli, F., and Combes, F. 1984, Astron.Ap., 140, L5.