Jianzu Wu Huiyu Xuan Optimal Timing of Firms' R&D Investment Under Asymmetric Duopoly: A Real Options and Game-Theoretic Approach. 122-131 2005 conf/aaim/2005 AAIM http://dx.doi.org/10.1007/11496199_15 db/conf/aaim/aaim2005.html#WuX05