1. Direct Uses of Geothermal Energy in 1990;Freeston;GRC Bull.,1990
2. Direct Uses of Geothermal Energy 1995;Freeston;Geothermics,1996
3. The Lindal Diagram;Gudmundsson;GRC Trans.,1985
4. Direct Uses of Earth Heat;Gudmundsson;Energy Research,1985
5. Geothermal Direct Use in the United States, update: 1990–1994;Lienau,1995