Haisch B.M., J.L. Linsky, O.B. Slee, D.R. Hearn, A.R. Walker, A.E. Rydgren, and G.D. Nicolson, The Astrophysical Journal 225, L35 (1978).
Walter F.M., A. Brown, J.L. Linsky, A.E. Rydgren, F.J. Vrba, M. Roth, L. Carrasco, P.F. Chugainov, N.I. Shakovskaya, and C.L. Imhoff, The Astrophysical Journal 314, 297 (1987).