The applications of the classical approach in a broad sense have been many, starting with the classical authors themselves, and present-day economists often inadvertently use a methodology which is closer to that of the classicals than to that of the neoclassicals. The relationship between intertemporal general equilibrium and models of prices of production deserves first to be clarified in this context. More specific applications include the extensions of input–output models to long-run prices and distribution, the analysis of joint production, with special extensions to energy analysis, to exhaustible resources and others. Finally, historical applications concern the analysis of technical progress and of different economic systems.