Yeh, Li-Ting, and Dong-Shang Chang. “Using Categorical DEA to Assess the Effect of Subsidy Policies and Technological Learning on R&D Efficiency of It Industry”. Technological and Economic Development of Economy, vol. 26, no. 2, Feb. 2020, pp. 311-30, https://doi.org/10.3846/tede.2019.11411.