@book{62147,
	author = {Kravis, Irving B and Heston, Alan},
	title = {A System of international comparisons of gross product and purchasing power},
	publisher = {John Hopkins University Press},
	year = {1975},
	address = {Baltimore},
	note = {Produced by the Statistical office of the United Nations the World Bank and the International Comparison unit of the Unit of the University of Pennsylvania}
}