fix broken reference links

source/concepts/faq.md

@@ -2,9 +2,11 @@
 
 ## Why are flakes controversial?
 
-Originally proposed in [RFC 49](https://github.com/NixOS/rfcs/pull/49), flakes have been in development since 2019.
+{ref}`Flakes <flakes>` were originally proposed in [RFC 49](https://github.com/NixOS/rfcs/pull/49), and have been in development since 2019.
 Nix introduced the implementation as its first [experimental feature] in 2021.
 
+[experimental feature]: https://nixos.org/manual/nix/unstable/contributing/experimental-features.html
+
 The subject is considered controversial among Nix users and developers in terms of design, development processes, and community governance.
 In particular:
 - The RFC was closed without conclusion, and some design and implementation issues are not yet resolved.
@@ -12,6 +14,8 @@ In particular:
 - The original implementation introduced [regressions](https://discourse.nixos.org/t/nix-2-4-and-what-s-next/16257) in the [Nix 2.4 release](https://nixos.org/manual/nix/stable/release-notes/rl-2.4.html), breaking some stable functionality without a [major version](https://semver.org/) increment.
 - New Nix users were and still are encouraged by various individuals to adopt flakes despite there being no concrete plan or timeline for stabilisation.
 
+[flake registry]: https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-registry.html
+
 This led to a situation where the stable interface was only sparsely maintained for multiple years, and repeatedly suffered breakages due to ongoing development.
 Meanwhile, the new interface was adopted widely enough for evolving its design without negatively affecting users to become very challenging.
 

source/concepts/flakes.md

@@ -1,3 +1,4 @@
+(flakes)=
 # Flakes
 
 What is usually referred to as "flakes" is: