The Nilo-Saharan language stock has six branches: Songhai (spoken in Mali), Saharan (including languages spoken both near Lake Chad, as in Kanuri, and in central Sahara), Maban (a group of tongues found E of Lake Chad), Furian (comprising only Fur, an important language of Sudan), Koman (a group of languages of Ethiopia and Sudan), and Chari-Nile, the principal branch of Nilo-Saharan, composed of the Eastern Sudanic languages, the Central Sudanic languages, and two additional tongues, Kunama and Berta; the Chari-Nile tongues are spoken in Sudan, Congo (Kinshasa), Uganda, Cameroon, Chad, the Central African Republic, Kenya, mainland Tanzania, and Ethiopia. The Eastern Sudanic subdivision of Chari-Nile itself has ten branches, the two most important of which are Nubian and Nilotic, both found in Sudan. Nubian is unique among modern African languages in that it has written texts of the medieval period. The Nilotic tongues include Shilluk, Dinka, Nuer, Masai, Turkana, Nandi, and Suk. The Central Sudanic subdivision of Chari-Nile consists of a number of languages, among them Mangbetu, spoken in Congo (Kinshasa), and Efe, used by the pygmies. Like the Niger-Congo languages, most of the Nilo-Saharan languages use tones; some Nilo-Saharan tongues inflect their nouns according to case, and still others have gender. The verb in many Nilo-Saharan languages has a system of verb derivation.