APA (7th ed.) Citation

Illinois State Geological Survey & Frye, J. C. (1969). Glacial tills of Northwestern Illinois. [publisher not identified].

Chicago Style (17th ed.) Citation

Illinois State Geological Survey and John C. Frye. Glacial Tills of Northwestern Illinois. Urbana: [publisher not identified], 1969.

MLA (9th ed.) Citation

Illinois State Geological Survey and John C. Frye. Glacial Tills of Northwestern Illinois. [publisher not identified], 1969.