Nickels, William G.
Understanding business
McGraw-Hill, 2008
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Chalmer, Bruce J.
Understanding statistics
Marcel Dekker, 1987
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Volpe, E. Peter (Erminio Peter)
Understanding evolution
Universal Books Stall, 1996"
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Corwin, Edward S.
Understanding the constitution
William Sloane, 1949
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Corwin, Edward S.
Understanding the constitution
United States of America, 1960
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