@article{7971,
      author = {Hollop, Edward E.},
      url = {http://library.usi.edu/record/7971},
      title = {Requirements for roll-over protective structures and  falling object protective structures for surface coal mines  and surface areas of underground coal mines /},
      publisher = {U.S. Dept. of the Interior, Mining Enforcement and Safety  Administration,},
      recid = {7971},
      pages = {56 p. :},
      address = {[Washington] :},
      year = {1977},
}