@book{971,
	author = {Black. John Donald},
	title = {Introduction to economics for agriculture / },
	publisher = {Macmillan. },
	year = {1953.},
	address = {New York : },
	url = {http://catalog.loc.gov/vwebv/holdingsInfo?searchId=244&recCount=25&recPointer=1&bibId=9316847}
}