Ryukyuan languages (known as Shimakutuba) are spoken in the Ryukyu Islands (Amami Islands, Okinawa Islands, Miyako Islands, and Yaeyama Islands). In 2009, UNESCO recognized 6 Ryukyuan languages as endangered in their Atlas of the World’s Languages in Danger.
The 6 Ryukyuan languages are often categorized into Northern and Southern Ryukyuan languages. The Northern Ryukyuan languages include Amami, Okinawan, and Kunigami. The Southern Ryukyuan languages include Miyako, Yaeyama, and Yonaguni. Currently, Amami, Okinawan, Kunigami, and Miyako are considered definitely endangered, and Yaeyama and Yonaguni are considered severely endangered.
Handbook of the Ryukyuan languages: History, Structure, and Use by 
沖繩語辞典 by うちなーぐち活用辞典 (Dictionary of the Practical Use of Okinawan) by 南琉球宮古語多良間方言辞典 (Dictionary of the Southern Ryukyu Miyako Language Tarama Dialect) by 沖繩語辞典 (A Dictionary of the Ryukyuan Language) by 
