3Connolly R A, Hirschey M.Firm size and the effect of R&D on Tobin's q[J].R&D Management, 2005,35 (2) : 217-223.
4HALL B H, ORIANIB R .Does the market value R&D investment by European firms? Evidence from a panel of manufac- turing firms in France, Germany, and Italy[J]. Ineternational of Industrial Organization, 2006,24(5) :971-993.