원문: [[https://scholar.google.co.kr/scholar?cluster=1149395920911360081&hl=ko&as_sdt=2005&sciodt=0,5|구글 스칼라]] 노트: [[https://drive.google.com/open?id=1IurUzVF9DdsREtxNAlMPhw9nPu0mmClG|노트]] {{youtube>k7LfZ9-ud9c?large}}