A named school-grammar of Korean cited in the source, such as a National Institute of Korean Language description of word classes, or a standard university morphology text.
Quirk, R., Greenbaum, S., Leech, G., & Svartvik, J. (1985). A comprehensive grammar of the English language. Longman; or another named English reference grammar used in the source.
Sohn, Ho-Min (1999). The Korean language. Cambridge University Press, for typological contrasts if cited.