References
From Why start at x, y, z
A History of Mathematical Notations by Florian Cajori.
Jeff Miller maintains some pages on the earliest known uses of mathematical words and mathematical symbols, as well as a list of ambiguities encountered at high school.
Christian Lawson-Perfect collects links to papers, books and other stuff about notation and conventions.
Common Errors in College Mathematics
The Digital Library of Mathematical Functions' notation section
Most ambiguous and inconsistent phrases and notations in maths on math.stackexchange
