Coombs, William E., author
McGraw-Hill, 1984
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Mott, Charles H.
John Wiley & Sons, 1981
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Coombs, William E.
F.W. Dodge Co. , 1958
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Goodlad, J.B., author
Heinemann, 1974
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Reiner, Laurence E., author
Prentice-Hall, 1972
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