http://www.google.co.kr/search?sourceid=chrome&ie=UTF-8&q=dispatch_async#q=dispatch_async&hl=ko&lr=lang_ko&newwindow=1&tbs=lr:lang_1ko&prmd=ivnsul&ei=rb6CTuaNHK6CmQWkhtFS&start=30&sa=N&bav=on.2,or.r_gc.r_pw.&fp=446ab16377526f55&biw=1207&bih=941
http://lab.smoon.kr/74
http://nol2soft.com/2011/08/15/blocks-blocks-and-variables-using-blocks/
http://meteorstudio.tistory.com/tag/multitasking
http://jeremyko.cafe24.com/jeremyko/entry/Grand-Central-Dispatch-Part-II-Multi-Core-Performance-%EC%9A%94%EC%95%BD?TSSESSIONjeremykocafe24com=1af048326631eef723ffc3d94f12ffb3