<!ENTITY null "<constant>NULL</constant>">
<!ENTITY c "<computeroutput>C</computeroutput>">
<!ENTITY defsystem "<application>defsystem</application>">
+<!ENTITY asdf "<application>ASDF</application>">
<!ENTITY bookinfo SYSTEM "bookinfo.sgml">
<!ENTITY preface SYSTEM "preface.sgml">
<!ENTITY intro SYSTEM "intro.sgml">