https://legacy.nationalcoreindicators.org/upload/core-indicators/NCI_DataBrief_Jan2014_042015.pdf
https://online.utpb.edu/about-us/articles/communication/how-much-of-communication-is-nonverbal/
https://www.ecfr.gov/current/title-42/chapter-IV/subchapter-C/part-441/subpart-G/section-441.301
https://www.ncbi.nlm.nih.gov/books/NBK470404/