Investopedia were pretty sure they were: https://web.archive.org/web/20171230012928/https://www.investopedia.com/terms/o/oligopoly.asp https://web.archive.org/

Investopedia were pretty sure they were: https://web.archive.org/web/20171230012928/https://www.investopedia.com/terms/o/oligopoly.asp https://web.archive.org/web/20171230012928/https://www.inves...