1. Baade, W. and Minkowski, R., 1937, Astrophys. J., 86, 123.
2. Bless, R.C., Code, A.D. and Houck, T.E., 1968, Astrophys. J., 153, 561.
3. Bless, R.C. and Savage, B.D., 1970, in L. Houziaux and H.E. Butler (eds.) Ultraviolet Stellar Spectra and Groundbased Observations, D. Reidel.
4. Bless, R.C. and Savage, B.D., 1972, Astrophys. J., 171, 293.
5. Borgman, J., 1961, Bull. Astr. Inst. Netherlands, 16, 99.