Document the last change (refs with citeproc) in manual.

MANUAL.txt

@@ -6487,7 +6487,7 @@ comma will be added if appropriate.)  Thus:
 ## Placement of the bibliography
 
 If the style calls for a list of works cited, it will be placed
-in a div with id `refs`, if one exists:
+in a div with id `refs`, if one exists:[^note-on-refs]
 
     ::: {#refs}
     :::
@@ -6496,6 +6496,13 @@ Otherwise, it will be placed at the end of the document.
 Generation of the bibliography can be suppressed by setting
 `suppress-bibliography: true` in the YAML metadata.
 
+[^note-on-refs]:
+    Note that if `--file-scope` is used, a div written this way will be
+    given an identifier of the form `FILE__refs`, to avoid duplicate
+    identifiers (see `--file-scope`). In view of this possibility,
+    pandoc will place the bibliography in any div whose identifier is
+    `refs` *or* ends with `__refs`.
+
 If you wish the bibliography to have a section heading, you can
 set `reference-section-title` in the metadata, or put the heading
 at the beginning of the div with id `refs` (if you are using it)