ZHANG, Ruda December 30, 2018:  Escape dollar sign. [0e7c576]
Ruda Zhang May 04, 2017:  Restructure econ notes [39e3490]
Ruda Zhang May 04, 2017:  Add newlines to Chinese full stop. [d4945fa]
Ruda Zhang June 26, 2016:  flatten repo structure with manual /category indexing [6dbf2d2]