CoreText（好文章链接）

http://www.jianshu.com/p/dacb99506bb9

http://www.jianshu.com/p/7c604e08dd6b

http://blog.csdn.net/smking/article/details/39646083

http://www.cocoachina.com/industry/20140521/8504.html

http://www.padovo.com/blog/2013/01/31/study-coretext/