Determination of ash in coals unusually high in calcite and pyrite,

At head of title: State of Illinois, Dwight H. Green, governor. Dept. of registration and education, Frank G. Thompson, director. Division of the State geological survey, M.M. Leighton, chief, Urbana."Reprinted from Industrial and engineering chemistry, analytical edition, vol. 14, no. 3, March 15, 1942.""Literature cited": p. 10