diff --git a/src/Doc/Demo_Easychair/ROOT b/src/Doc/Demo_Easychair/ROOT
--- a/src/Doc/Demo_Easychair/ROOT
+++ b/src/Doc/Demo_Easychair/ROOT
@@ -1,11 +1,11 @@
-chapter Doc
+chapter Doc  (*Isabelle documentation*)
 
 session Demo_Easychair (doc) = HOL +
-  options [document_variants = "demo_easychair"]
+  options [document_variants = "demo_easychair"]  (*Isabelle documentation*)
   theories
     Document
   document_files (in "$ISABELLE_EASYCHAIR_HOME")
     "easychair.cls"
   document_files
     "root.bib"
     "root.tex"
diff --git a/src/Doc/Demo_FoilTeX/ROOT b/src/Doc/Demo_FoilTeX/ROOT
--- a/src/Doc/Demo_FoilTeX/ROOT
+++ b/src/Doc/Demo_FoilTeX/ROOT
@@ -1,13 +1,13 @@
-chapter Doc
+chapter Doc  (*Isabelle documentation*)
 
 session Demo_FoilTeX (doc) = HOL +
-  options [document_variants = "demo_foiltex",
+  options [document_variants = "demo_foiltex",  (*Isabelle documentation*)
     document_build = "pdflatex", document_logo = "FoilTeX"]
   theories
     Document
   document_files (in "$ISABELLE_FOILTEX_HOME")
     "fltfonts.def"
     "foil20.clo"
     "foils.cls"
   document_files
     "root.tex"