http://www.myoops.org/twocw/mit/NR/rdonlyres/Sloan-School-of-Management/15-433InvestmentsSpring2003/B374D154-334B-46FB-B1ED-2C3D23C48B2E/0/154338Equity_tw.pdf
http://www.gxtvu.com.cn/eduwest/web_courseware/accountancy/0177/3/3.htm
http://www.gxtvu.com.cn/eduwest/web_courseware/accountancy/0177/3/3.htm
http://www.gxtvu.com.cn/eduwest/web_courseware/accountancy/0177/3/3.htm
http://www.gxtvu.com.cn/eduwest/web_courseware/accountancy/0177/3/3.htm