@misc{indiciae1d99c493e45b,
  title = {Relations among surficial materials, light intensity, and sycamore-seed germination along the Potomac River near Washington, D.C.},
  author = {Robert S. Sigafoos},
  year = {1976},
  url = {https://pubs.usgs.gov/publication/70233435},
  note = {Source identifier: 70233435}
}