Found in articles
pp. 7166–23 Admiral Badger, Naval Hero, Dies: Retired Head of Eastern Sea Frontier Won Medal Of Honor —Led Flotilla Into Tokyo (PDF). The New York Times
a Washington insider's memoir of events. Courtwright, David T. Sky as frontier: adventure, aviation, and empire 2005. Texas A&M University Press. 2005
器铭文中也有发现，如1930年在河南汲县出土的西周早期青铜器小臣誺簋的铭文中出现了“海”字。 英文中用“海”与“洋”的英文分别是“sea”和“ocean”。其中，“sea”可以追溯到古英语。由中古英语開始，表示广义意思時需要加上冠词。“Ocean”则可追溯到古希腊语中的Ōkeanós。
2019: 83 [11 August 2020]. ISBN 9780190070915. Elizabeth Gaspar Brown, "Frontier Justice: Wayne County 1796–1836", in Essays in Nineteenth-Century American
Culture - Retrieved 3 September 2011. Robert Guisepi - The Ottomans: From Frontier Warriors To Empire Builders （页面存档备份，存于互联网档案馆） - 1992 - History World International