. . "Illinois State Geological Survey." . . "Geology, Stratigraphic." . . "Palynology Illinois." . . "Palynology." . . "Coal Geology Illinois." . . "Coal Geology." . . "Illinois." . . "Hulls Geología E.U.A Illinois." . . "Geología estratigráfica Pensilvano." . . "Pennsylvanian Geologic Period." . . "Palinología E.U.A Illinois." . . "From 280 to 310 million years ago" . . "Stratigraphic correlation Illinois." . . "Stratigraphic correlation." . . "Correlation and palynology of coals in the Carbondale and Spoon formations (Pennsylvanian) of the northeastern part of the Illinois Basin" . "Correlation and palynology of coals in the Carbondale and Spoon formations (Pennsylvanian) of the northeastern part of the Illinois Basin"@en . . . . . . . . . . . . . . . . . . . . . "Correlation and palynology of coals in the Carbondale and Spoon formations (Pennsylvanian) of the Northeastern part of the Illinois Basin" . . . "Correlation and palynology of coals in the Carbondale and Spoon Formations (Pennsylvania) of the Northeastern part of the Illinois Basin" . . . . . . . . "Correlation and palynology of coals in the carbondale and spoon formations, Pennsylvanian, of the north-eastern part of the Illinois Basin" . . . . . . . . . "Geology, Stratigraphic Pennsylvanian." . .