^Gregory and Stuart, Paul and Robert (February 28, 2013). The Global Economy and its Economic Systems. South-Western College Pub. m/s. 30. ISBN978-1285055350. There are three broad forms of property ownership – private, public, and collective (cooperative).
^Bertrand Badie; Dirk Berg-Schlosser; Leonardo Morlino (2011). International Encyclopedia of Political Science. SAGE Publications, Inc. m/s. 2132. ISBN978-1412959636. Private property cannot exist without a political system that defines its existence, its use, and the conditions of its exchange. That is, private property is defined and exists only because of politics.