1. See https://www.genengnews.com/the-lists/the-top-15-best-selling-drugs-of-2017/77901068.
2. See http://www.businessinsider.com/common-popular-prescription-drugs-us-2017-7.
3. Top drugs and companies by sales in 2017
4. See http://pharmaceuticalcommerce.com/business-and-finance/global-drug-spending-was-1-135-trillion-in-2017-says-iqvia/.
5. See https://www.statista.com/statistics/272181/world-pharmaceutical-sales-by-region/.