ZHANG, Ruda December 30, 2018:  Use dollar style math markup. [1b7036c]
ZHANG, Ruda December 03, 2018:  Test GFM: checked box, emoji. (Not working) [9878ca5]
Ruda Zhang August 07, 2016:  Replace tab with two spaces. [adaa87b]
Ruda Zhang June 26, 2016:  Use present/absent/absolut/default link coloring. [6e7e216]
Ruda Zhang June 26, 2016:  use canonical filename and no internal H1 [eeca8ff]