@article{241496,
      note = {Distributed to some depository libraries in microfiche.},
      author = {Rytuba, James J. and Cox, Dennis P.},
      url = {http://library.usi.edu/record/241496},
      title = {Porphyry gold : a supplement to U.S. Geological Survey  bulletin 1693 /},
      publisher = {U.S. Geological Survey,},
      recid = {241496},
      pages = {7 leaves :},
      address = {Menlo Park, CA :},
      year = {1991},
}