diff --git a/doc/src/sgml/isn.sgml b/doc/src/sgml/isn.sgml
new file mode 100644
index 4a2e7da..c1da702
*** a/doc/src/sgml/isn.sgml
--- b/doc/src/sgml/isn.sgml
*************** SELECT isbn13(id) FROM test;
*** 364,370 ****
     The prefixes used for hyphenation were also compiled from:
     <itemizedlist>
      <listitem><para><ulink url="http://www.gs1.org/productssolutions/idkeys/support/prefix_list.html"></ulink></para></listitem>
!     <listitem><para><ulink url="http://www.isbn-international.org/en/identifiers.html"></ulink></para></listitem>
      <listitem><para><ulink url="http://www.ismn-international.org/ranges.html"></ulink></para></listitem>
     </itemizedlist>
  
--- 364,372 ----
     The prefixes used for hyphenation were also compiled from:
     <itemizedlist>
      <listitem><para><ulink url="http://www.gs1.org/productssolutions/idkeys/support/prefix_list.html"></ulink></para></listitem>
!     <listitem><para><ulink url="http://en.wikipedia.org/wiki/List_of_ISBN_identifier_groups"></ulink></para></listitem>
!     <listitem><para><ulink url="https://www.isbn-international.org/content/isbn-users-manual"></ulink></para></listitem>
!     <listitem><para><ulink url="http://en.wikipedia.org/wiki/International_Standard_Music_Number"></ulink></para></listitem>
      <listitem><para><ulink url="http://www.ismn-international.org/ranges.html"></ulink></para></listitem>
     </itemizedlist>