A number of multilateral treaties exist to outlaw four major classes of WMDs: biological, chemical, nuclear, and radiological. Such treaties include the Biological Weapons Convention (BWC) and the Chemical Weapons Convention (CWC). Multilateral treaties targeting the proliferation, testing and achieving progress on the disarmament of nuclear weapons include the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the Partial Test Ban Treaty (PTBT), and the Comprehensive Nuclear-Test-Ban Treaty, which was signed in 1996 but has yet to enter into force. Several treaties also exist to prevent the proliferation of missiles and related technologies, which can be used as a vehicle to deliver WMD payloads. These treaties include the Hague Code of Conduct (HCOC) and the Missile Technology Control Regime (MTCR).