@misc{indiciae26209dc6b664,
  title = {Unary and binary multisystems: Topologic classification of phase diagrams and relation to Euler's theorem on polyhedra},
  author = {E. H. Roseboom and E-An Zen},
  year = {1982},
  doi = {10.2475/ajs.282.3.286},
  url = {https://pubs.usgs.gov/publication/70011804},
  note = {Source identifier: 70011804}
}