diff --git a/doc/ctlseqs.texi b/doc/ctlseqs.texi
index 0336dac..7494c7f 100644
--- a/doc/ctlseqs.texi
+++ b/doc/ctlseqs.texi
@@ -26,7 +26,6 @@ Texts.  A copy of the license is included in the section entitled
 @titlepage
 @title ctlseqs
 @subtitle Helper Library for Control Sequences, version @value{VERSION}
-
 @author CismonX
 
 @page
@@ -39,12 +38,25 @@ Texts.  A copy of the license is included in the section entitled
 @summarycontents
 @contents
 
-
+@ifnottex
 @node Top
 @top ctlseqs
 
 This manual is for ctlseqs, a helper library for control sequences.
 
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the @pxref{GNU Free Documentation License}, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts.
+
+ctlseqs is free software. You can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the
+Free Software Foundation, either version 3 of the License, or (at your option)
+any later version.
+@end ifnottex
+
+
 @menu
 * Overview:: Brief overview of ctlseqs.
 * Control Sequence Matching:: Using ctlseqs for matching control sequences.
@@ -54,13 +66,26 @@ This manual is for ctlseqs, a helper library for control sequences.
 
 Appendices
 
-* API Reference:: C API reference of ctlseqs.
+* API Reference:: C API reference for ctlseqs.
+* GNU Free Documentation License:: Copying conditions of this manual.
 
 @end menu
 
+
 @node Overview
 @chapter Overview of ctlseqs
 
+The name ``ctlseqs'' is an abbreviation of ``control sequences'', as defined
+in section 5.4 of ECMA-48.
+
+As the name suggests, this library focuses on handling control sequences.
+However, it only cares about the bit combinations, while the actual meaning
+and implementation of a control sequence is up to the user.
+
+The C API provided by ctlseqs is composed of three major parts: The
+helper macros, the control sequence matcher, and the control sequence reader.
+Any of them can be used separatedly or combined.
+
 
 @node Control Sequence Matching
 @chapter Control Sequence Matching
@@ -82,4 +107,10 @@ Appendices
 @appendix API Reference
 
 
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
+
+@include fdl.texi
+
+
 @bye