@misc{Calkins_Frank_Cathcart_Bulletin,
 author={Calkins, Frank Cathcart},
 copyright={Gdańsk University of Technology Library},
 howpublished={online},
 publisher={Government Printing Office.},
 language={eng},
 title={Bulletin 640-D. Molybdenite and nickel ore in San Diego County California},
 type={journal},
 keywords={geology, mineralogy, United States of America, journals},
}