Chinese commentary about a Sun Tzu quotation
A simple Google search for 'art of war': 


  http://classics.mit.edu/Tzu/artwar.html
  
  The Art of War
  
  By Sun Tzu
  
  XIII. The Use of Spies
  
  
  Hence the use of spies, of whom there are five classes: (1) Local spies; (2) inward spies; (3) converted spies; (4) doomed spies; (5) surviving spies.
  


故用間有五 - Hence there are five classes of spies

有鄉間 -  there are Local spies

有內間 - there are inward spies

有反間 - there are converted spies

有死間 - there are doomed spies

有生間 - there are surviving spies

You can read the explanation on the five kinds of spies on that web-page