diff --git a/documentation/content/en/books/fdp-primer/asciidoctor-primer/_index.adoc b/documentation/content/en/books/fdp-primer/asciidoctor-primer/_index.adoc
--- a/documentation/content/en/books/fdp-primer/asciidoctor-primer/_index.adoc
+++ b/documentation/content/en/books/fdp-primer/asciidoctor-primer/_index.adoc
@@ -219,7 +219,7 @@
 ====
 
 [[asciidoctor-links-internal]]
-=== Internal link
+=== Links to another book or article
 
 To point to another book or article the Asciidoctor variables should be used.
 For example, if we are in the `cups` article and we want to point to `ipsec-must` these steps should be used.
@@ -240,6 +240,43 @@
 +
 extref:{ipsec-must}[IPSec-Must article]
 
+[NOTE]
+====
+The `extref` macro is defined as an extension.
+It is designed to render the correct link across the different outputs
+====
+
+=== Links to the same file or to another file in the same book
+
+Books are structured in different directories to keep a sane layout.
+To create a link from one subdirectory of a book to another subdirectory of the
+same book, use the `crossref` macro:
+....
+crossref:doc-build[documentation-makefile]
+....
+And this would be rendered as
+
+crossref:doc-build[documentation-makefile, This link]
+
+[NOTE]
+====
+The `crossref` macro is defined as an extension.
+It is designed to render the correct link across the different outputs
+====
+
+[NOTE]
+====
+Use the `crossref` macro for intra-document links too.
+Although it might be inconvenient to write the name of the current document,
+it ensures the correct link is renderedacross the different outputs
+====
+
+[WARNING]
+====
+Do not use neither the `xref` macro nor its shortcut `<<` `>>`.
+They do not work well in all output formats.
+====
+
 [[asciidoctor-images-icons]]
 == Images and Icons