1. Theory of the ground pipe heat source for the heat pump;Ingersoll;ASHVE Trans,1948
2. Conduction of heat in solids;Carslaw,1959
3. Heat conduction with engineering, geological and other applications;Ingersoll,1954
4. Simulation of vertical U-tube ground-coupled heat pump systems using the cylindrical heat source solution;Deerman;ASHRAE Trans,1991
5. Eskilson P. Thermal analysis of heat extraction boreholes. PhD thesis. Sweden: University of Lund; 1987.