"The powers of external sovereignty on the part of the State do not depend on the affirmative grant of this in the Constitution. ... The State would not be completely sovereign if it did not have in common with other members of the family of nations the right and power in the field of international relations equal to the right and power of other states. These powers of the State include the power to declare war or to participate in a war, to conclude peace, to make treaties, and maintain diplomatic relations with other states." — Crotty v An Taoiseach (1987) IESC 4 (9 April 1987)
Shaw, Malcolm Nathan (2003). International law. Cambridge University Press. p.178. Article 1 of the Montevideo Convention on Rights and Duties of States, 1933 lays down the most widely accepted formulation of the criteria of statehood in international law. It note that the state as an international person should possess the following qualifications: '(a) a permanent population; (b) a defined territory; (c) government; and (d) capacity to enter into relations with other states'
Jasentuliyana, Nandasiri, บ.ก. (1995). Perspectives on international law. Kluwer Law International. p.20. So far as States are concerned, the traditional definitions provided for in the Montevideo Convention remain generally accepted.
Wheaton, Henry (1836). Elements of international law: with a sketch of the history of the science. Carey, Lea & Blanchard. p.51. A sovereign state is generally defined to be any nation or people, whatever may be the form of its internal constitution, which governs itself independently of foreign powers.
"sovereign", The American Heritage Dictionary of the English Language (4thed.), Houghton Mifflin Company, 2004, สืบค้นเมื่อ 21 February 2010, adj. 1. Self-governing; independent: a sovereign state.
"sovereign", The New Oxford American Dictionary (2nded.), Oxford: Oxford University Press, 2005, ISBN0-19-517077-6, adjective ... [ attrib. ] (of a nation or state) fully independent and determining its own affairs.
Chen, Ti-chiang. The International Law of Recognition, with Special Reference to Practice in Great Britain and the United States. London, 1951.
Crawford, James. The Creation of States in International Law. Oxford University Press, 2005. ISBN 0-19-825402-4, pp.15–24.
Lauterpacht, Sir Hersch. Recognition in International Law. Cambridge, U.K., 1947.
Raič, D. Statehood and the Law of Self-determination. Martinus Nijhoff Publishers, 2002. ISBN 978-90-411-1890-5. p 29 (with reference to Oppenheim in International Law Vol. 1 1905 p110)