<ul><li><a href=https://www.upu.int/en/Universal-Postal-Union/About-UPU/Member-Countries?csid=-1&cid=111#mb--1 target=_blank>Universal Postal Union Website - Estonia</a></li><li><a href=https://www.konkurentsiamet.ee/en/postal-communications-railways/postal-communications/overview target=_blank>Estonian Competition Authority(Overview of postal communications)</a></li></ul>