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The first author was supported in part by a grant from the National Science Foundation. The present address of the second author is Morehead State University, Morehead, Kentucky 40351.
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Deutsch, F., Lindahl, R.J. Minimal extremal subsets of the unit sphere. Math. Ann. 197, 251–278 (1972). https://doi.org/10.1007/BF01428200
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DOI: https://doi.org/10.1007/BF01428200