1. Appell, H. R., Miller, R. D., and Wender, I. (1972). “On the Mechanism of Lignite Liquefaction with Carbon Monoxide and Water,” presented before Div. Fuel Chem., 163rd National Meeting, Am. Chem. Soc., April 10–14, 1972.
2. “Coal Liquefaction with Synthesis Gas,”;Appell,1979