https://www.guru99.com/association-aggregation-composition-difference.html
https://brownbears.tistory.com/511
https://stackoverflow.com/questions/52231702/uml-sequence-diagram-auto-numbering-in-visual-paradigm
https://www.geeksforgeeks.org/unified-modeling-language-uml-sequence-diagrams/
https://www.nextree.co.kr/p6753/