1. The geography of the United states in the year 2000;Berry,1975
2. Positive externalities and the public provision of transportation infrastructure: An evolutionary perspective;Blum;Journal of Transportation and Statistics,1998
3. The innovator’s dilemma: When new technologies cause great firms to fail;Christensen,1997
4. Estimates of world GDP, one million B.C.—present;De Long,1998