@article{198503,
      note = {Distributed to depository libraries in microfiche.},
      author = {Carroll, R. D. and Magner, J. E.},
      url = {http://library.usi.edu/record/198503},
      title = {A portable vacuum hammer seismic source for use in tunnel  environments [microform] /},
      publisher = {U.S. Dept. of the Interior, Geological Survey :},
      recid = {198503},
      pages = {ii, 18, A17 p. :},
      address = {Denver, Colo. :},
      year = {1993},
}