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In passing, I firmly believe that research should be offset by a certain amount of teaching, if only as a change from the agony of research. The trouble, however, I freely admit, is that in practice you get either no teaching, or else far too much.
"The Mathematician's Art of Work" in Bela Bollobas (ed.) Littlewood's Miscellany, Cambridge: Cambridge University Press, 1986.
When a Number System Loses Uniqueness: The Case of the Maya
 Ascher, M., Before the Conquest, Mathematics Magazine, Vol. 65, No. 4, Oct., 1992, pp. 211-218.
 Cooke, R., The History of Mathematics: A Brief Course, 2nd ed., Wiley-Interscience, John Wiley & Sons, 2005.
 Katz, V. J., A History of Mathematics: An Introduction, 3rd ed., Addison-Wesley, 2009, p. 270.
 Morley, S. G., An Introduction to the Study of the Maya Hieroglyphs, 57, Smithsonian Institution Bureau of American Ethnology, Government Printing Office, 1915. Also available from Google Books.
 Maya Info: Ring and Serpent Dates in the Dresden Codex, www.mayainfo.org/works/ring/default.asp
 Mundo Maya: Mayan Codices, www.mayadiscovery.com/ing/history/codices.htm
 The Maya Astronomy Page: Maya Calendar, www.michielb.nl/maya/calendar.html
 Maya Exploration Center, http://mayaexploration.com/staff_barnhart.php
Maya Calendar Conversions, by Ximena Catepillan and Waclaw Szymanski (2010)
Maya Cycles of Time, by Sandra Monteferrante (2007)
Shell-Gellasch, Amy and Pedro J. Freitas, "When a Number System Loses Uniqueness: The Case of the Maya," Loci (May 2012), DOI: 10.4169/loci003883