Tweak the expressions in AUTHORS.

AUTHORS

@@ -12,10 +12,10 @@ Authors of XZ Utils
     The SHA-256 implementation in liblzma is based on code written by
     Wei Dai in Crypto++ Library <https://www.cryptopp.com/>.
 
-    Some scripts have been adapted from gzip. The original versions
-    were written by Jean-loup Gailly, Charles Levert, and Paul Eggert.
-    Andrew Dudman helped adapting the scripts and their man pages for
-    XZ Utils.
+    A few scripts have been adapted from GNU gzip. The original
+    versions were written by Jean-loup Gailly, Charles Levert, and
+    Paul Eggert. Andrew Dudman helped adapting the scripts and their
+    man pages for XZ Utils.
 
     The initial version of the threaded .xz decompressor was written
     by Sebastian Andrzej Siewior.
@@ -30,9 +30,24 @@ Authors of XZ Utils
       - Jonathan Nieder
       - Joachim Henke
 
-    The GNU Autotools-based build system contains files from many authors,
-    which I'm not trying to list here.
+    Many people have contributed improvements or reported bugs.
+    Most of these people are mentioned in the file THANKS.
 
-    Several people have contributed fixes or reported bugs. Most of them
-    are mentioned in the file THANKS.
+    The translations of the command line tools and man pages have been
+    contributed by many people via the Translation Project:
+
+      - https://translationproject.org/domain/xz.html
+      - https://translationproject.org/domain/xz-man.html
+
+    The authors of the translated man pages are in the header comments
+    of the man page files. In the source package, the authors of the
+    translations are in po/*.po and po4a/*.po files.
+
+    Third-party code whose authors aren't listed here:
+
+      - GNU getopt_long() in the 'lib' direcotry is included for
+        platforms that don't have a usable getopt_long().
+
+      - The build system files from GNU Autoconf, GNU Automake,
+        GNU Libtool, GNU Gettext, Autoconf Archive, and related files.