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https://en.wikipedia.org/wiki/Global_Internet_usage4
2. Comparison of the usage of Default sub domain www vs. Default protocol https for websites, W3Techs, 21 May 2018.
https://w3techs.com/technologies/details/ce-httpsdefault
3. Anonymity, Privacy and Security Online, Pew Research Center, 5 September 2013.
http://www.pewinternet.org/2013/09/05/anonymity-privacy-and-security-online/
4. Elkhatib, Y., Tyson, G., Welzl, M.: Can SPDY really make the web faster? In: 2014 IFIP Networking Conference, pp. 1–9. IEEE, June 2014
5. Belshe, M., Peon, R.: SPDY Protocol., draft-mbelshe-httpbis spdy-00, February 2012.
https://tools.ietf.org/html/draft-mbelshe-httpbis-spdy-00