https://www.rulesofsport.com/sports/sumo-wrestling.html
https://www.japan-guide.com/sumo/rules.html
https://www.usasumo.com/learn/rules-techniques/
https://theculturetrip.com/asia/japan/articles/japanese-sumo-wrestling-everything-you-need-to-know/
https://wayofmartialarts.com/college-collegiate-wrestling-everything-you-need-to-know/
https://www.sportshistoryweekly.com/stories/us-sumo-open-wrestling-japan-andrew-freund-byamba,974