@article{12020,
      author = {Willman, H. B. and Kolata, Dennis R.,},
      url = {http://library.usi.edu/record/12020},
      title = {The Platteville and Galena groups in northern Illinois /},
      publisher = {Illinois State Geological Survey,},
      recid = {12020},
      pages = {75 p. :},
      address = {Urbana :},
      year = {1978},
}