@article{60992,
      note = {Cover title.},
      author = {Willman, H. B.},
      url = {http://library.usi.edu/record/60992},
      title = {Rock stratigraphy of the Silurian system in northeastern  and northwestern Illinois},
      publisher = {Illinois State Geological Survey,},
      recid = {60992},
      pages = {55 p.},
      address = {Urbana,},
      year = {1973},
}