Boggess A., R.C. Bohlin, D.C. Evans, H.R. Freeman, T.R. Gull, S.R. Heap, D.A. Klinglesmith, G.R. Longanecker, W. Sparks, D.K. West, and A.V. Holm, Nature 275, 377-385 (1978).
Brown A., M.V. Penston, R. Johnstone, C. Jordan, N.P.M. Kuin, M.T.V.T. Lago, B.D. Gross, and J.L. Linsky, in (NASA, 1984).