[SR-Users] "Command not found" error during "make install"

Hi, I faced the following error during installing "sip-router" by command "make install" after successful compilation by command "make all". I will appreciate you so much if you can shed light on. My system is 32 bit Fedora. Thanks in advance. Youngjin install -m 644 README /usr/local/share/doc/ser/ docbook2x-man -s ../../doc/stylesheets/serdoc2man.xsl auth.xml make[1]: docbook2x-man: Command not found make[1]: *** [auth.7] Error 127 make: [modules-man] Error 1 (ignored) docbook2x-man -s ../../doc/stylesheets/serdoc2man.xsl auth_db.xml make[1]: docbook2x-man: Command not found make[1]: *** [auth_db.7] Error 127 make: [modules_s-man] Error 1 (ignored) make[1]: `sercmd' is up to date.