diff --git a/Rakefile b/Rakefile
index 7878929..3e6ef30 100644
--- a/Rakefile
+++ b/Rakefile
@@ -72,7 +72,7 @@ end
 
 task html: ["html/index.html"]
 
-file "html/index.html" => htmlfilenames do
+file "html/index.html" => htmlfilenames+["html/tfetextview_doc.html"] do
   buf = [ "# Gtk4 Tutorial for beginners\n", "\n" ]
   src2md "src/abstract.src.md", "html/abstract.md", -1
   File.open("html/abstract.md") do |file|
@@ -96,6 +96,11 @@ file "html/index.html" => htmlfilenames do
   add_head_tail_html "html/index.html"
 end
 
+file "html/tfetextview_doc.html" => "src/tfetextview/tfetextview_doc.md" do
+  sh "pandoc -o html/tfetextview_doc.html src/tfetextview/tfetextview_doc.md"
+  add_head_tail_html "html/tfetextview_doc.html"
+end
+
 0.upto(srcfiles.size - 1) do |i|
   html_md = "html/#{srcfiles[i].to_md}"
   html_html = "html/#{srcfiles[i].to_html}"
@@ -131,8 +136,8 @@ end
 
 task latex: ["latex/main.tex"]
 
-file "latex/main.tex" => ["latex/abstract.tex"] + texpathnames do
-  gen_main_tex "latex", texfilenames
+file "latex/main.tex" => ["latex/abstract.tex", "latex/tfetextview_doc.tex"] + texpathnames do
+  gen_main_tex "latex", texfilenames, ["tfetextview_doc.tex"]
 end
 
 file "latex/abstract.tex" => "src/abstract.src.md" do
@@ -141,6 +146,10 @@ file "latex/abstract.tex" => "src/abstract.src.md" do
   File.delete("latex/abstract.md")
 end
 
+file "latex/tfetextview_doc.tex" => "src/tfetextview/tfetextview_doc.md" do
+  sh "pandoc -o latex/tfetextview_doc.tex src/tfetextview/tfetextview_doc.md"
+end
+
 0.upto(srcfiles.size - 1) do |i|
   file "latex/#{srcfiles[i].to_tex}" => (srcfiles[i].c_files << srcfiles[i].path) do
     src2md srcfiles[i].path, "latex/#{srcfiles[i].to_md}", 86
diff --git a/doc/Readme_for_developers.md b/doc/Readme_for_developers.md
index 472c92d..8e8bdb8 100644
--- a/doc/Readme_for_developers.md
+++ b/doc/Readme_for_developers.md
@@ -149,17 +149,23 @@ Other words or expressions may be available in the future version.
 
 ## Conversion
 
-The @@@ commands are carried out by scripts src2md.rb.
-In addition, some conversion is made by srd2md.rb.
+The @@@ commands are carried out by `src2md.rb`.
+In addition, some conversion is made by `src2md.rb`.
 
 - Relative links are changed according to the change of base directory.
-- Size option in image link is left out when the destination is GFM or html.
-- Relative link is left out when the destination is latex.
+- Size option in image link is removed when the destination is GFM or html.
+- Relative link is removed when the destination is latex.
 - Lines in fence code block are folded when the destination is latex.
 
-There's a method `src2md` in the `lib/lib_src2md.rb` script.
+There's a method `src2md` in the `lib/lib_src2md.rb`.
 This method converts src.md file into md file.
-This method is used in `srd2md.rb` and `Rakefile`.
+The script `src2md.rb` just invokes this method.
+In the same way, the method is called in the action in `Rakefile`.
+
+The code analyzing @@@if series command in the method is rather complicated.
+It is based on the state diagram below.
+
+![state diagram](../image/state_diagram.png)
 
 ## Directory structure
 
diff --git a/gfm/sec12.md b/gfm/sec12.md
index 8db1f1f..a0fe78d 100644
--- a/gfm/sec12.md
+++ b/gfm/sec12.md
@@ -391,7 +391,10 @@ However, in Gtk4, `gtk_dialog_run`is unavailable any more.
 The important thing is to duplicate `tv->file`.
 Otherwise, if the caller frees the GFile object, `tv->file` is no more guaranteed to point the GFile.
 
-## Source file of tfetextview.c
+## API document and source file of tfetextview.c
+
+Refer [API document of TfeTextView](../src/tfetextview/tfetextview_doc.md).
+It is under the directory `src/tfetextview`.
 
 All the source files are listed in [Section 15](sec15.md).
 You can find them under [src/tfe5](../src/tfe5) and [src/tfetextview](../tfetextview) directories.
diff --git a/image/state_diagram.png b/image/state_diagram.png
new file mode 100644
index 0000000..9909b52
Binary files /dev/null and b/image/state_diagram.png differ
diff --git a/image/state_diagram.xcf b/image/state_diagram.xcf
new file mode 100644
index 0000000..5822432
Binary files /dev/null and b/image/state_diagram.xcf differ
diff --git a/lib/lib_gen_main_tex.rb b/lib/lib_gen_main_tex.rb
index 2e239f6..f9e1272 100644
--- a/lib/lib_gen_main_tex.rb
+++ b/lib/lib_gen_main_tex.rb
@@ -1,7 +1,7 @@
 # lib_gen_main_tex.rb
 #  -- Library ruby script to generate main.tex.
 
-def gen_main_tex directory, texfilenames
+def gen_main_tex directory, texfilenames, appendixfilenames
   #  parameter: directory: the destination directory to put generated files.
   #             texfilenames: an array of latex files. Each of them is "secXX.tex" where XX is digits.   
 
@@ -22,7 +22,7 @@ int main(int argc, char **argv) {
 ~~~
 EOS
 
-  File.open("sample.md", "w") { |f| f.print sample_md }
+  File.write "sample.md", sample_md
   if (! system("pandoc", "-s", "-o", "sample.tex", "sample.md"))
     raise ("pandoc retuns error status #{$?}.\n")
   end
@@ -30,21 +30,19 @@ EOS
   sample_tex.gsub!(/\\documentclass\[[^\]]*\]{[^}]*}/,"")
   sample_tex.gsub!(/\\usepackage\[[^\]]*\]{geometry}/,"")
   sample_tex.gsub!(/\\usepackage\[[^\]]*\]{graphicx}/,"")
+  sample_tex.gsub!(/\\setcounter{secnumdepth}{-\\maxdimen} % remove section numbering/,"")
   sample_tex.gsub!(/\\author{[^}]*}/,"")
   sample_tex.gsub!(/\\date{[^}]*}/,"")
   preamble = []
-  in_preamble = true
   sample_tex.each_line do |l|
-    if in_preamble
-      if l =~ /\\begin{document}/
-        in_preamble = false
-      elsif l != "\n"
-        preamble << l
-      end
+    if l =~ /\\begin{document}/
+      break
+    elsif l != "\n"
+      preamble << l
     end
   end
-  preamble << "\\usepackage[margin=2.4cm]{geometry}"
-  preamble << "\\usepackage{graphicx}"
+  preamble << "\\usepackage[margin=2.4cm]{geometry}\n"
+  preamble << "\\usepackage{graphicx}\n"
   File.write("#{directory}/helper.tex",preamble.join)
   File.delete("sample.md")
   File.delete("sample.tex")
@@ -70,6 +68,11 @@ EOS
   texfilenames.each do |filename|
     main += "  \\input{#{filename}}\n"
   end
+  main += "\\newpage\n"
+  main += "\\appendix\n"
+  appendixfilenames.each do |filename|
+    main += "  \\input{#{filename}}\n"
+  end
   main += "\\end{document}\n"
   IO.write("#{directory}/main.tex", main)
 end
diff --git a/src/sec12.src.md b/src/sec12.src.md
index d2e6272..c94a463 100644
--- a/src/sec12.src.md
+++ b/src/sec12.src.md
@@ -205,7 +205,18 @@ tfetextview/tfetextview.c tfe_text_view_get_file
 The important thing is to duplicate `tv->file`.
 Otherwise, if the caller frees the GFile object, `tv->file` is no more guaranteed to point the GFile.
 
-## Source file of tfetextview.c
+## API document and source file of tfetextview.c
+
+@@@if gfm
+Refer [API document of TfeTextView](tfetextview/tfetextview_doc.md).
+It is under the directory `src/tfetextview`.
+@@@elif html
+Refer [API document of TfeTextView](../html/tfetextview_doc.html).
+Its original markdown file is under the directory `src/tfetextview`.
+@@@elif latex
+Refer API document of TfeTextView in the appendix.
+Its original markdown file is under the directory `src/tfetextview`.
+@@@end
 
 All the source files are listed in [Section 15](sec15.src.md).
 You can find them under [src/tfe5](tfe5) and [src/tfetextview](../tfetextview) directories.
diff --git a/src/tfetextview/tfetextview_doc.md b/src/tfetextview/tfetextview_doc.md
index 82e68c6..cca958c 100644
--- a/src/tfetextview/tfetextview_doc.md
+++ b/src/tfetextview/tfetextview_doc.md
@@ -1,4 +1,4 @@
-# TfeTextView
+# TfeTextView API reference
 
 TfeTextView -- Child widget of GtkTextView. It holds GFile the contents of GtkTextBuffer correponds to.