@misc{indiciaeb68d53a73da2,
  title = {Modelling the evolution of human trail systems.},
  author = {D Helbing and J Keltsch and P Molnár},
  year = {1997},
  doi = {10.1038/40353},
  url = {https://pubmed.ncbi.nlm.nih.gov/9214501/},
  note = {Source identifier: 9214501}
}