src/Pure/Thy/bibtex.ML

           val bibtex_entries = Resources.theory_bibtex_entries thy_name;
           val _ =
             if null bibtex_entries andalso thy_name <> Context.PureN then ()
             else
               citations |> List.app (fn (name, pos) =>
-                if member (op =) bibtex_entries name then ()
+                if member (op =) bibtex_entries name orelse name = "*" then ()
                 else error ("Unknown Bibtex entry " ^ quote name ^ Position.here pos));
 
           val kind = Config.get ctxt cite_macro;
           val location = Document_Output.output_document ctxt {markdown = false} loc;
         in Latex.cite {kind = kind, citations = citations, location = location} end));