ZHANG, Ruda March 23, 2018:  Global remove trailing whitespaces [2b7ff90]
Ruda Zhang June 27, 2016:  use absolute link in books. [fb966a0]
Ruda Zhang June 26, 2016:  add category tag to wiki pages [a9b356c]
Ruda Zhang June 26, 2016:  Use internal link for wiki pages. [22daaba]