Higgins, P. M. (2008). Number story: From counting to cryptography. Copernicus Books.
Chicago-čujuhus (17. p.)Higgins, Peter M. Number Story: From Counting to Cryptography. London: Copernicus Books, 2008.
MLA-čujuhus (9. p.)Higgins, Peter M. Number Story: From Counting to Cryptography. Copernicus Books, 2008.
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