21.3 References

1. Thomas Hillegass, http://uscampgrounds.info (a word version of the contents of this site is provided on the 2023 NEI Supplemental nonpoint data FTP site)
2. How Much Firewood is in a Cord? And Other Important Firewood Questions, https://lumberjax.com/how-much-firewood-is-in-a-cord/ (a word version of the contents of this site is provided on the 2023 NEI Supplemental nonpoint data FTP site)