@misc{indiciae60affce48993,
  title = {Chemical composition of igneous rocks expressed by means of diagrams, with reference to rock classification on a quantitative chemico-mineralogical basis},
  author = {J. P. Iddings},
  year = {1903},
  doi = {10.3133/pp18},
  url = {https://pubs.usgs.gov/publication/pp18},
  note = {Source identifier: pp18}
}