The Court's jurisdiction was largely optional, but there were some situations in which they had "compulsory jurisdiction", and states were required to refer cases to them. That came from three sources: the Optional Clause of the League of Nations, general international conventions and "special bipartite international treaties". The Optional Clause was a clause attached to the protocol establishing the court and required all signatories to refer certain classes of dispute to the court, with compulsory judgments resulting. There were approximately 30 international conventions under which the Court had similar jurisdiction, including the Treaty of Versailles, the Air Navigation Convention, the Treaty of St. Germain and all mandates signed by the League of Nations. It was also foreseen that there would be clauses inserted in bipartite international treaties, which would allow the referral of disputes to the Court; that occurred, with such provisions found in treaties between Czechoslovakia and Austria, and between Czechoslovakia and Poland.