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REFERENCES

  1. M. L. Humason, N. U. Mayall, and A. R. Sandage, A.J., 61, 97, 1956.
  2. M. L. Humason, Ap. J., 83, 10, 1936.
  3. W. W. Morgan, Pub. A.S.P., 68, 509, 1956.
  4. Y. Öhman, Ap. J., 80, 171, 1934.
  5. H. W. Babcock, Lick Obs. Bull., 19, 41, 1939 (No. 498).
  6. N. U. Mayall and L. H. Aller, Ap. J., 95, 5, 1942.
  7. Reported by I. S. Bowen, A.J., 61, 339, 1956.
  8. W. Baade, Pub. Michigan Obs., 10, 10, 1951.
  9. W. A. Baum and M. Schwarzschild, A.J., 60, 247, 1955.