Article 16 Vienna Convention on Diplomatic Relations
1.Heads of mission shall take precedence in their respective classes in the order of the date and time of taking up their functions in accordance with article 13.
2.Alterations in the credentials of a head of mission not involving any change of class shall not affect his precedence.
3.This article is without prejudice to any practice accepted by the receiving State regarding the precedence of the representative of the Holy See.
See also: Article 15 Vienna Convention on Diplomatic Relations