SAS PROC 用户指南
方便查询
http://support.sas.com/documentation/cdl/en/proc/61895/HTML/default/viewer.htm#titlepage.htm
http://support.sas.com/documentation/onlinedoc/91pdf/sasdoc_913/base_proc_8977.pdf
http://www.okstate.edu/sas/v8/sashtml/proc/index.htm