ZHANG, Ruda March 03, 2021:  Use mathcal for big O notation, to distinguish from the orthogonal group. [69caae9]
ZHANG, Ruda January 18, 2020:  Convert math-text words to text only when the math symbols are ASCII only. [e4c945c]
ZHANG, Ruda April 22, 2019:  More on learning theory. [b8a2256]
ZHANG, Ruda February 21, 2019:  More on SVD, CUR. [e2f9299]
ZHANG, Ruda October 04, 2018:  Corrections to manifold learning [3da1eb0]
ZHANG, Ruda September 30, 2018:  CSS redesign; more edits. [dd44d96]
ZHANG, Ruda October 15, 2017:  separate econometrics and regression inference [b2083ef]
ZHANG, Ruda October 14, 2017:  Merge computational and statistical learning. [a493a55]