1. Marking HTTP as Non-secure. https://www.chromium.org/Home/chromium-security/marking-http-as-non-secure
2. Project Sonar. https://www.rapid7.com/research/project-sonar/
3. SSL Certificates - Rapid7 Open Data. https://opendata.rapid7.com/sonar.ssl/
4. Scanning All the Things (2013). https://blog.rapid7.com/2013/09/26/internet-wide-probing-rapid7-sonar/
5. Baseline Requirements for the Issuance and Management of Publicly-Trusted Certificates (2020). https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.7.0.pdf