Etymology of the Japanese word fude. 論文 S. Yoshitake ·1930-02-01 ·『Bulletin of the School of Oriental and African Studies』 6(1) pp. 45-53 doi:10.1017/s0041977x00090947
Linguistics and language policies in North Korea 論文 Chin-Wu Kim ·1978-01-01 ·『Korean studies』 2(1) pp. 159-175 doi:10.1353/ks.1978.0002