International law, sometimes called the law of nations, has evolved over the last 400 years. The three major sources of international law according to Article 38 of the Statute of the International Court of Justice are: international conventions or treaties; international customs; and the general principles of law as recognized by civilized nations. The Permanent Court of Arbitration was established by the Hague Conferences of 1899 and 1907, and the Permanent Court of International Justice was set up in 1921 and succeeded in 1946 by the International Court of Justice. Since World War II international organizations such as the UN and its related bodies have contributed to the expansion and increased scope of international law to include political and strategic affairs, economic, social, communications, and environmental matters. By the 1990s international law had shown its durability and flexibility by expanding to cover new areas of world relations, and its efficacy through the machinery of the UN.