Directory of Illinois mineral operators, to accompany mineral industries map, September 1, 1920.
Comp. by H. P. Christensen.

APA Citation

Illinois State Geological Survey., Christensen, H. P. (Henrietta Petrea). (1921). Directory of Illinois mineral operators, to accompany mineral industries map, September 1, 1920. Urbana: Printed by authority of the State of Illinois [Schnepp & Barnes, Printers, Springfield].

MLA Citation

Illinois State Geological Survey, and H. P. (Henrietta Petrea) Christensen. Directory of Illinois Mineral Operators, to Accompany Mineral Industries Map, September 1, 1920. Urbana: Printed by authority of the State of Illinois [Schnepp & Barnes, Printers, Springfield], 1921.