<!ENTITY url.windows2000 "http://www.microsoft.com/windows2000/">
<!ENTITY url.windows2003server "http://www.microsoft.com/windowsserver2003/default.mspx">
<!ENTITY url.netbsd "http://www.netbsd.org/">
<!ENTITY url.openbsd "http://www.openbsd.org/">
<!ENTITY url.ubuntu "http://www.ubuntu.com/">
<!ENTITY url.docbook "http://docbook.org/">
<!ENTITY url.windows2000 "http://www.microsoft.com/windows2000/">
<!ENTITY url.windows2003server "http://www.microsoft.com/windowsserver2003/default.mspx">
<!ENTITY url.netbsd "http://www.netbsd.org/">
<!ENTITY url.openbsd "http://www.openbsd.org/">
<!ENTITY url.ubuntu "http://www.ubuntu.com/">
<!ENTITY url.docbook "http://docbook.org/">