https://en.wikipedia.org/wiki/Zodiac_Killer
https://www.britannica.com/biography/Zodiac-killer
http://www.zodiackillerfacts.com
https://www.thoughtco.com/the-zodiac-killer-972167
https://www.oxygen.com/martinis-murder/who-was-the-zodiac-killer-brutal-slayings-disturbing-ciphers-suspects
https://www.upi.com/Top_News/US/2019/08/13/Viacom-CBS-agree-to-all-stock-merger-deal/8731565726544/
https://www.psychologytoday.com/us/blog/wicked-deeds/201506/serial-killers-modus-operandi-signature-staging-posing
https://www.thecrimemag.com/journey-inside-twisted-mind-zodiac-killer/
https://www.history.com/news/the-zodiac-killer-a-timeline
https://www.history.co.uk/shows/the-zodiac-killer-case-closed/articles/the-biggest-unsolved-crime-in-american-history
https://medium.com/@charlierusso23/why-has-dna-evidence-not-yet-unmasked-the-zodiac-killer-26ed5cac40f3
https://web.archive.org/web/20111015111536/http://blog.sfgate.com/djennings/2009/10/07/40-years-of-zodiac-the-cold-case-that-haunts-dave-toschi/
https://www.quora.com/How-was-the-Zodiac-killer-able-to-evade-the-police-How-did-this-serial-killer-operate-Why-was-this-cold-case-never-solved-during-the-investigation
http://www.thefinertimes.com/Serial-Killers/the-worst-kind-of-serial-killer.html