APA-referens (7:e uppl.)

Ingram, G. K., & Liu, Z. (1998). Vehicles, roads, and road use: Alternative empirical specifications. World Bank.

Chicago-referens (17:e uppl.)

Ingram, Gregory K., och Zhi Liu. Vehicles, Roads, and Road Use: Alternative Empirical Specifications. Washington, D.C: World Bank, 1998.

MLA-referens (9:e uppl.)

Ingram, Gregory K., och Zhi Liu. Vehicles, Roads, and Road Use: Alternative Empirical Specifications. World Bank, 1998.