In this paper we show a method for solving in closed form a particular family of four-dimension non-linear modified Hamiltonian dynamic systems, with two states and two co-states, which arises from a twosector endogenous growth model where the physical capital stock is combined with a renewable natural capital stock as essential inputs for production.
Aznar-Márquez, J., & Ruiz-Tamarit, J. (2002). Closed-Form Solution for a Two-Sector Endogenous Growth Model with two Controls (ECON Working Papers 2002/30). https://hdl.handle.net/2078.5/35570