References
Wordstream. (2020). What is Google Ads?. https://www.wordstream.com/articles/what-is-google-adwords
Webfx. (2020). How much does Google Ads cost?. https://www.webfx.com/blog/marketing/much-cost-advertise-google-adwords/
Wordstream. (2020). How Does Google Make Its Money: The 20 Most Expensive Keywords in Google Ads. https://www.wordstream.com/articles/most-expensive-keywords