McClintock W.E., H.W. Moos, R.C. Henry, J.L. Linsky, and E.S. Barker, The Astrophysical Journal Supplement Series 37, 223 (1978).
Robinson E.L., E.S. Barker, A.L. Cochran, W.D. Cochran, and R.E. Nather, The Astrophysical Journal 251, 611 (1981).