RedHat provides an extensive explanation of certificates, what they are, and how they authenticate web sites, servers, clients, or people.
The Linux Documentation Project provides a “how to” about SSL certificates.
Durumeric, Kasten, Bailey, and Halderman presented 2013 results of a large-scale analysis of certificates actively used by SSL/TLS sites.
The Comodo delegation failure was widely covered in the tech media.
Describes how root certificate authorities delegate certificate signing to third party resellers, and how such certificates are validated.
Video notes: cys.me/vid/c15
The previous video describes how browsers handle multiple certificate authorities for validating public-key certificates vimeo.com/208879048
See the entire Cryptosmith series in its album vimeo.com/album/4229550