 However the theory became very important to neo-Marxists such as Ernest Mandel and Cyrus Bina who interpreted late capitalism as a form of increasingly parasitic rentier capitalism in which surplus profits are obtained by capitalists from monopolising the access to resources, assets and technologies under conditions of imperfect competition.Marxist writers such as Cyrus Bina have extended the concept of rents to oil rents.Marx's main texts on rent theory can be found in the second (edited) volume of "Theories of Surplus Value" and in Part 6 of "Capital, Volume III".