https://emflag.com/blog/the-significance-and-history-of-flying-at-halfstaff/
https://study.com/academy/lesson/why-are-flags-put-at-half-mast.html
https://laws.boe.gov.sa/BoeLaws/Laws/LawDetails/03de5462-eda0-4dd6-9efa-a9a700f1f802/1
https://www.archives.gov/federal-register/codification/proclamations/03044.html
