1Lutz H. Equipment Investment and Growth in Developing countries.Journal of Development Economics, 2000(61):335-364
2Xu Jincheng, Hao Weichang, Kou Xinli, et al. Research and Development of the Object-oriented Life Cycle Assessment Database.Materials and Design, 2001(22):101-105
3Frederic C, AIban C. Logical Foundations of Multilevel Databases.Data & Knowledge Engineering, 1999(29):259-291