1. icloud private relay overview. https://www.apple.com/privacy/docs/iCloud_Private_Relay_Overview_Dec2021.PDF
2. PCM: Click fraud prevention and attribution sent to advertiser. https://webkit.org/blog/11940/pcm-click-fraud-prevention-and-attribution-sent-to-advertiser/. Accessed 3 Sept 2021
3. Trust tokens. https://developer.chrome.com/docs/privacy-sandbox/trust-tokens/
4. VPN by google one, explained. https://one.google.com/about/vpn/howitworks
5. Lecture Notes in Computer Science;M Abe,2001