1/ The response by the community was amazing. You guys are great! Especially the ones who are nitpicking and fact checking me! I love it. http://cnd.mcgill.ca/~ivan/miniref/HN_wave_Jan1_Jan2.png
2/ By popular demand, I created a PDF version of the book -- mostly changed the font and added more space on each page. Preview is here: http://cnd.mcgill.ca/~ivan/miniref/noBSmath_preview.pdf PDF is available on gumroad: http://gum.co/noBSmath
3/ Will write up a detailed post about the experience later today here: http://minireference.com/blog/
4/ The notation "∈" stands for "is an element of" and is covered later on in the book. See http://cnd.mcgill.ca/~ivan/miniref/set_notation.pdf for more info.
Thank you everyone for the feedback and the support.