Social Web

• Webring [Wikipedia]
• Linkback [Wikipedia]
• Refback [Wikipedia]
• Trackback [Wikipedia]
• Pingback [Wikipedia]
• indieweb.org/POSSE
• ActivityPub [W3]

Webmention

• en.wikipedia.org/wiki/Webmention
• w3.org/TR/webmention
• indieweb.org/Webmention-faq
• indieweb.org/Webmention

Security & Spam

• w3.org/TR/webmention/#webmention-verification-p-4
• indieweb.org/Vouch