diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml
new file mode 100644
index 1d7d95f..685351f
*** a/doc/src/sgml/pgbuffercache.sgml
--- b/doc/src/sgml/pgbuffercache.sgml
***************
*** 84,90 ****
        <entry><structfield>relforknumber</structfield></entry>
        <entry><type>smallint</type></entry>
        <entry></entry>
!       <entry>Fork number within the relation</entry>
       </row>
  
       <row>
--- 84,91 ----
        <entry><structfield>relforknumber</structfield></entry>
        <entry><type>smallint</type></entry>
        <entry></entry>
!       <entry>Fork number within the relation;  see
!       <filename>include/storage/relfilenode.h</></entry>
       </row>
  
       <row>
***************
*** 98,104 ****
        <entry><structfield>usagecount</structfield></entry>
        <entry><type>smallint</type></entry>
        <entry></entry>
!       <entry>Page LRU count</entry>
       </row>
  
      </tbody>
--- 99,105 ----
        <entry><structfield>usagecount</structfield></entry>
        <entry><type>smallint</type></entry>
        <entry></entry>
!       <entry>Clock-sweep access count</entry>
       </row>
  
      </tbody>