diff --git a/Makefile b/Makefile
index 4b77479..8857f31 100644
--- a/Makefile
+++ b/Makefile
@@ -18,9 +18,17 @@ MATH_FORMULAS = --webtex
 CSS_FILE = style.css
 CSS_ARGS = --css=$(CSS_FILE)
 
-# FILTER_ARGS = --filter pandoc-crossref
+# Debugging
+
 # DEBUG_ARGS = --verbose
 
+# Pandoc filtes - uncomment the following variable to enable cross references filter. For more
+# information, check the "Cross references" section on the README.md file.
+
+# FILTER_ARGS = --filter pandoc-crossref
+
+# Combined arguments
+
 ARGS = $(TOC) $(MATH_FORMULAS) $(CSS_ARGS) $(METADATA_ARGS) $(FILTER_ARGS) $(DEBUG_ARGS)
 PANDOC_COMMAND = pandoc
 
diff --git a/chapters/01-introduction.md b/chapters/01-introduction.md
index ee79247..cbdc78b 100644
--- a/chapters/01-introduction.md
+++ b/chapters/01-introduction.md
@@ -17,9 +17,9 @@ A bigger seagull:
 This is the second subsection.
 
 
-Please, check [First] subsection.
+Please, check [First: Images] subsection.
 
-Please, check [this](#first) subsection.
+Please, check [this](#first-images) subsection.
 
 | Index | Name |
 | ----- | ---- |