1. Theory of earth heat exchangers for the heat pump;Ingersoll;Trans. Am. Soc. Heating Ventilating Engrs,1951
2. Solar energy in Canada. U.N.;Alcott,1961
3. Analysis of a proposed solar-earth heat pump;Penrod,1964
4. Conserving energy with heat storage wells;Meyer;Environmental Science and Technology,1973
5. Calculations on a solar-earth heat pump system for residential use;Graven,1973