Yortsos, Y. C. Modification of chemical and physical factors in steamflood in increase heavy oil recovery. Annual report, October 1, 1994--September 30, 1995, report, October 1996; (https://digital.library.unt.edu/ark:/67531/metadc679158/m1/1/: accessed October 18, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .