Parks, B. C., & O'Donnell, H. J. (1956). Petrography of American coals. Washington, DC.: U.S. Government Printing Office.
Παραπομπή Chicago StyleParks, Bryan C., and H. J. O'Donnell. Petrography of American Coals. Washington, DC.: U.S. Government Printing Office, 1956.
Παραπομπή MLAParks, Bryan C., and H. J. O'Donnell. Petrography of American Coals. Washington, DC.: U.S. Government Printing Office, 1956.
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