@misc{indiciaee2ad2f1216fe,
  title = {Philadelphia region input-output study working papers},
  author = {Isard, W. and Langford, T. W., Jr. and Romanoff, E.},
  year = {1968},
  url = {https://ntrs.nasa.gov/citations/19680017281},
  note = {Source identifier: 19680017281}
}