ZHANG, Ruda February 24, 2019:  Fix PDF links [72277e6]
ZHANG, Ruda March 23, 2018:  Global remove trailing whitespaces [2b7ff90]
Ruda Zhang June 26, 2016:  add category tag to wiki pages [a9b356c]
Ruda Zhang June 26, 2016:  use canonical filename and no internal H1 [eeca8ff]