@misc{indiciae90b9b02203c9,
  title = {George Engelmann : botanical notebook 9 : Echinocereus, Cereus, Eulychnia, Pilocereus — Illustration, [No.] 2131 1},
  year = {1869},
  url = {https://www.biodiversitylibrary.org/page/56133145},
  note = {Source identifier: page-56133145}
}