<!ENTITY configurations                     SYSTEM "Configurations.docbook">
<!ENTITY configurations-ppp                 SYSTEM "Configurations/Ppp.docbook">
<!ENTITY configurations-ppp-intro           SYSTEM "Configurations/Ppp/intro.docbook">
<!ENTITY configurations-ppp-modem-install   SYSTEM "Configurations/Ppp/modem-install.docbook">
<!ENTITY configurations-ppp-modem-config    SYSTEM "Configurations/Ppp/modem-config.docbook">