Specific Gravity Studies of Illinois coal : Nebel, Merle L[ouis]

von Nebel, Merle Louis
Veröffentlicht 1916

Geology and mineral resources of the La Harpe and Good Hope quadrangles

von Savage, Thomas Edmund
Veröffentlicht in State of Illinois, Department of Registration and Education, Div. of the State Geological Survey ; Bulletin Nr 43 (1921)