Single on Where ten HTTP header fields are defined

I found all ten definitions and read each section on rfc-editor.org.

• RFC 9111, "HTTP Caching", defines Age (§5.1), Cache-Control (§5.2) and Expires (§5.3): https://www.rfc-editor.org/rfc/rfc9111.html
• RFC 9110, "HTTP Semantics", defines Last-Modified (§8.8.2), ETag (§8.8.3), Location (§10.2.2), Retry-After (§10.2.3) and Vary (§12.5.5): https://www.rfc-editor.org/rfc/rfc9110.html. These fields used to be defined in RFC 7231, 7232 and 7234. All three are now obsolete, so I didn't use them.
• RFC 6797, "HTTP Strict Transport Security (HSTS)", defines Strict-Transport-Security in §6.1. The page has no "Obsoleted by" notice: https://www.rfc-editor.org/rfc/rfc6797.html
• RFC 8288, "Web Linking", defines Link in §3. Its header says "Obsoletes: 5988" and has no "Obsoleted by" notice: https://www.rfc-editor.org/rfc/rfc8288.html

To decide whether an RFC is still current, I looked for an "Obsoleted by" notice in the header of each RFC page. I didn't check a separate status index such as the RFC Editor's errata or status pages. The RFC text wraps across lines, so each quote below is written on one line with single spaces.

{"answers":[
{"field":"Age","rfc":"9111","section":"5.1","quote":"The \"Age\" response header field conveys the sender's estimate of the time since the response was generated or successfully validated at the origin server.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Cache-Control","rfc":"9111","section":"5.2","quote":"The \"Cache-Control\" header field is used to list directives for caches along the request/response chain.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Expires","rfc":"9111","section":"5.3","quote":"The \"Expires\" response header field gives the date/time after which the response is considered stale.","url":"https://www.rfc-editor.org/rfc/rfc9111.html"},
{"field":"Last-Modified","rfc":"9110","section":"8.8.2","quote":"The \"Last-Modified\" header field in a response provides a timestamp indicating the date and time at which the origin server believes the selected representation was last modified, as determined at the conclusion of handling the request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"ETag","rfc":"9110","section":"8.8.3","quote":"An entity tag consists of an opaque quoted string, possibly prefixed by a weakness indicator.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Location","rfc":"9110","section":"10.2.2","quote":"The \"Location\" header field is used in some responses to refer to a specific resource in relation to the response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Retry-After","rfc":"9110","section":"10.2.3","quote":"Servers send the \"Retry-After\" header field to indicate how long the user agent ought to wait before making a follow-up request.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Vary","rfc":"9110","section":"12.5.5","quote":"The \"Vary\" header field in a response describes what parts of a request message, aside from the method and target URI, might have influenced the origin server's process for selecting the content of this response.","url":"https://www.rfc-editor.org/rfc/rfc9110.html"},
{"field":"Strict-Transport-Security","rfc":"6797","section":"6.1","quote":"The Strict-Transport-Security HTTP response header field (STS header field) indicates to a UA that it MUST enforce the HSTS Policy in regards to the host emitting the response message containing this header field.","url":"https://www.rfc-editor.org/rfc/rfc6797.html"},
{"field":"Link","rfc":"8288","section":"3","quote":"The Link header field provides a means for serialising one or more links into HTTP headers.","url":"https://www.rfc-editor.org/rfc/rfc8288.html"}
]}