The Kurds in Turkey (Kurdish: Kurdên li Tirkiye, Turkish: Türkiye'deki Kürtler) are an Indo-European people first mentioned in ancient Greek sources. Based on these sources it is believed that Kurds are remnants of ancient Cordueni who established an ancient Kingdom near modern-day Diyarbekir in the first century BC. Cordueni were under the cultural and religious influence of Hurrian. Most Kurds live in Turkey, where their numbers are estimated somewhere between 11,400,000 and 15,000,000 people. Both figures include Zaza people as Kurds. These figures are for the number of persons who identify as Kurds, not the number who speak a Kurdish language, since many self-identified Kurds speak only Turkish. Estimations based on mother tongue data leads various estimations of Kurdish population in Turkey ranging from 6% to 23%, Ibrahim Sirkeci claims the closest figure should be above 17.8% taking into account political context and as a result the potential bias in responses recorded in surveys and censuses. Today, most Kurds in Turkey live in big cities (like Istanbul) or in Southeastern Turkey . There are also Kurdish people living in Tunceli Province and in the Central Anatolia Region, concentrated to the west of Lake Tuz (Haymana, Cihanbeyli, Kulu, Yunak) and also scattered in districts like Alaca, Çiçekdağı, Yerköy, Emirdağ, and Zile. Traditional Kurdish-inhabited regions inside present Turkish borders are sometimes referred to as Turkish Kurdistan. According to a March 2007 survey, Kurmanjs and Zazas together comprise an estimated 13.4% of the adult population, and 15.68% of the whole population.Kurdish separatist armed movements such as the PKK and KADEK continue to mount actions threatening Turkey's national unity and are held responsible for approximately 35,000 casualties of civilians and troops over the past two decades.Between 1983 and 1991, it was forbidden to publicize, publish and/or Broadcast in any language other than Turkish, unless that language was the first official language of a country that Turkey has diplomatic relations with. Though this ban technically applied to any language, Kurdish, being the first official language of no country although widely spoken in the Kurdistan region, was to be the most affected.Turkey's treatment of its citizens of Kurdish origin has been a frequent subject of international criticism . Due to the size of their community, the Kurds are viewed as a threat to Turkey's national security. Kurds have largely resisted forcible assimilation policies of the government since 1930s. The main official strategy for assimilating the Kurds has been suppression of their language. Most Kurds have retained their native tongue, despite the governmental efforts over several decades to promote Turkish among them.