Dorfman (2008) "Marginal Productivity Theory" Dorfman, R. (2008). "Marginal Productivity Theory". In Palgrave Macmillan (ed.). The New Palgrave Dictionary of Economics. London: Palgrave Macmillan. pp. 1–5. doi:10.1057/978-1-349-95121-5_988-2. ISBN978-1-349-95121-5 – via SpringerLink.