diff --git a/index.html b/index.html
index b2004a8..e859454 100644
--- a/index.html
+++ b/index.html
@@ -4353,9 +4353,8 @@ hello-flake
 <div class="literalblock">
 <div class="content">
 <pre class="nowrap">$ cowsay "Moo!"
-bash: line 15: cowsay: command not found
+bash: line 17: cowsay: command not found
 $ nix develop
-warning: Git tree '/home/amy/codeberg/nix-book' is dirty
 $ cowsay "Moo!"
  ______
 &lt; Moo! &gt;
@@ -4957,7 +4956,7 @@ mkShell <span class="tok-p">{</span>
 </div>
 <div id="footer">
 <div id="footer-text">
-Last updated 2025-09-04 14:33:42 IST
+Last updated 2025-09-04 14:37:45 IST
 </div>
 </div>
 </body>
diff --git a/source/book.adoc b/source/book.adoc
index f4b8ad6..35b8589 100644
--- a/source/book.adoc
+++ b/source/book.adoc
@@ -1,5 +1,6 @@
 = Wombat's Book of Nix
 {authors}
+:doctype: book
 :sectnums:
 :toc: left
 :toclevels: 4
@@ -18,6 +19,14 @@ https://mhwombat.codeberg.page/nix-book/[online]
 and as a downloadable
 https://codeberg.org/mhwombat/nix-book/raw/branch/pages/wombats-book-of-nix.pdf[PDF].
 
+[preface]
+== Acknowledgments
+
+I would like to thank the patient people on the
+https://discourse.nixos.org/[NixOS Discourse Forum]
+who answered my many questions,
+especially `cdepillabout` and `FedericoSchonborn`.
+
 include::intro/main.adoc[leveloffset=+1]
 
 include::nix-language/main.adoc[leveloffset=+1]
diff --git a/source/recipes/devshell/tempwork/flake.lock b/source/recipes/devshell/tempwork/flake.lock
deleted file mode 100644
index 34e1406..0000000
--- a/source/recipes/devshell/tempwork/flake.lock
+++ /dev/null
@@ -1,60 +0,0 @@
-{
-  "nodes": {
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1731533236,
-        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1756992239,
-        "narHash": "sha256-S+U82sUdy7qpb5cx1iIAUt/zz63LduLm/U/9y68mmZk=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "5a17103f36c1eb08ae49f2f14cd6d181bf0b6fa7",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "flake-utils": "flake-utils",
-        "nixpkgs": "nixpkgs"
-      }
-    },
-    "systems": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}
diff --git a/source/recipes/devshell/tempwork/flake.nix b/source/recipes/devshell/tempwork/flake.nix
deleted file mode 100644
index 83db46c..0000000
--- a/source/recipes/devshell/tempwork/flake.nix
+++ /dev/null
@@ -1,20 +0,0 @@
-{
-  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs";
-    flake-utils.url = "github:numtide/flake-utils";
-  };
-
-  outputs = { self, nixpkgs, flake-utils }:
-    flake-utils.lib.eachDefaultSystem (system:
-      let
-        pkgs = import nixpkgs { inherit system; };
-      in
-      {
-        devShells = rec {
-          default = pkgs.mkShell {
-            packages = [ pkgs.cowsay ];
-          };
-        };
-      }
-    );
-}