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REFERENCES

  1. Abell, George O. 1958, Ap. J. Suppl., 3, 211 (No. 31).
  2. Baum, W. A. 1955, A.J., 60, 153.
  3. Holmberg, Erik. 1958, Lund Medd., 136.
  4. Morgan, W. W., and Mayall, N. U. 1957, Pub. A.S.P., 69, 291.
  5. Sandage, Allan, and Wallerstein, George. 1960, Ap. J., 131, 598.
  6. Sharpless, S. L. 1952, Ap. J., 116, 251.