Artikel 4

1. Subject to the provisions of Article 5, a Contracting State cannot claim immunity from the jurisdiction of the courts of another Contracting State if the proceedings relate to an obligation of the State, which, by virtue of a contract, falls to be discharged in the territory of the State of the forum.
2. Paragraph 1 shall not apply:
(a) in the case of a contract concluded between States;
(b) if the parties to the contract have otherwise agreed in writing;
(c) if the State is party to a contract concluded on its territory and the obligation of the State is governed by its administrative law.