Ref
텍스트 마이닝 기초
http://bigdata.dongguk.ac.kr/lectures/bigdata/_book/텍스트마이닝기초.html
https://blog-ko.superb-ai.com/the-hidden-treasures-of-nlp-and-text-mining/
https://www.ibm.com/kr-ko/topics/text-mining