7M.M.Parker, R.J.Benson, Information Economics [ M]. Prentice Hall, 1988.
8Hannua Kivjiarvi, Timo Saarinen, Investment in information systems and the financial Performance of the firm [ J ] .Infromration&Management, 1995 ( 28 ).
9Brian L.Dos Santos. Information Technology Investments: Characteristics, Choices, Market Risk and Value [ J ] . Information Systems Frontiers, 2003 ( 5 ).