1. Fedde, P. A.; Zavada, R. A.Solvent extraction of Kentucky tar sand in a 200 ton per day pilot plant. InInst of Gas Technology:Chicago, IL, USA, Louisville, KY, USA, 1983; pp563–578.
2. Babcock, R. E.; Daniel, R. D.; Herter, G. L.Herter solvent extraction process for the recovery of heavy oils and tars. InUNITAR/UNDP Information Cent for Heavy Crude & Tar Sands:New York, NY, USA, Long Beach, CA, USA, 1985; Vol.2, pp1054–1066.