Sigurdsson, O.; Steingrimsson, B.S. & Stefansson, V. PRESSURE BUILDUP MONITORING OF THE KRAFLA GEOTHERMAL FIELD, ICELAND, article, January 22, 1985; (https://digital.library.unt.edu/ark:/67531/metadc882618/m1/1/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .