	More specialized definitions of RH supplies have also been formulated. One of these is WHO's Interagency List of Essential Medicines for Reproductive Health (2006), which reflects the current international consensus on essential medicines for the provision of quality RH services. Because the list prioritizes medicines believed to address the most pressing public health problems, it is by definition, selective. Nonetheless, it does include a broad range of contraceptives, drugs to prevent and treat sexually transmitted diseases and HIV/AIDS, and medicines to ensure healthy pregnancy and delivery. The Interagency List is a subset of the WHO Model List of Essential Medicines, updated every two years since 1977. The 17th edition of the Essentials Medicines List (EML) was last published in 2011. To assist countries who formulate their own lists of essential RH supplies, based on local needs, the Coalition partners WHO, UNFPA and PATH published the Essential Medicines for Reproductive Health: Guiding Principles for their inclusion on National Medicines Lists (2006) .