1. Chum, H.L., Johnson, D.K., Black, S., Ratcliff, M. and Goheen, D.W., Lignin hydrotreatment to low-molecular-weight compounds. In Advances in Solar Energy, ed. K.W. Böer, American Solar Energy Soc., Boulder CO and Plenum Press, New York, 1988, pp. 91–200.
2. Bridgwater, A.V., and Kuester, J.L. (eds.) Research in Thermochemical Biomass Conversion, Elsevier Appl. Sci., London, New York, 1988.
3. Soltes, E.J. and Milne, T.A., Pyrolysis Oils from Biomass, Producing, Analyzing, and Upgrading. ACS Symp. Series 376, American Chemical Society, Washington, D.C., 1988
4. McKeough, P., Nissilä, M., Solantausta, Y., Beckman, D. and Östman, A., Technoeconomic assessment of direct biomass liquefaction processes. Research report no. 337 from the Technical Research Centre of Finland (VIT), Espoo, 1985.
5. Meier, D. and Rupp, M., Direct Catalytic Liquefaction Technology of Biomass–Status and Review. In Biomass Pyrolysis Liquids Upgrading and Utilization, ed. A.V. Bridgwater and G. Grassi, Elsevier Appl. Sci., London, 1991, 93–102.