https://nts2.arrl.org/ntsgte-an-aprs-nts-gateway/
https://www.arrl.org/table-of-contents-nts-methods-and-practices-guidelines
https://radiorelay.org/files/reference/TrafficNets.pdf
https://outpostpm.org/docs/NTS-14.pdf (sending NTS by packet radio)
https://ema.arrl.org/packet-procedures/
http://www.felge.us/tfctools.html
http://www.felge.us/Packet2.pdf