1. R. Davis Jr., J.C. Evans, B.T. Cleveland, Proc. Int. Neutrino Conf. Purdue, 53(1978)
2. R. Davis Jr., priv. communication (1980).
3. A.W. Wolfendale, E.C.M. Young, and R. Davis Jr., Nature, Phys. Sci. 238, 130(1972).
4. E.L. Fireman, Proc. Int. Cosmic Ray Conf., Kyoto, Vol. 12 (1979).
5. J.N. Bahcall, S.H. Lubow, W.F. Huebner, N.H. Magee Jr., A.L. Merts, M.F. Argo, P.D. Parker, B. Rozsnyai, and R.K. Ulrich, Phys. Rev. Lett. 45, 945(1980).