*Beckwith (2007): "Koguryo, the Language of Japan's Continental Relatives: An Introduction to the Historical-Comparative Study of the Japanese-Koguryoic Languages, with a Preliminary Description of Archaic Northeastern Middle Chinese.
* Beckwith (2007): "Koguryo, the Language of Japan’s Continental Relatives: An Introduction to the Historical-Comparative Study of the Japanese-Koguryoic Languages, with a Preliminary Description of Archaic Northeastern Middle Chinese.