A multilateral export control regime is an informal group of like-minded supplier countries that seek to contribute to the non-proliferation of weapons of mass destruction, delivery systems, and advanced conventional weapons through national implementation of guidelines and control lists for exports. For a chart of national membership in different regimes, see the SIPRI Yearbook chapter on "Transfer controls". There are currently four such regimes: While not formally an export control regime, the Zangger Committee has developed guidance on nuclear export restrictions required by the Non-Proliferation Treaty (NPT). The following 30 countries are members of all of the above four regimes: The following 13 countries are members of at least three of these regimes: The following two countries are members of at least two of these regimes: The following five countries and political entities are members of at least one of these regimes: