diff --git a/README.org b/README.org
index e5dd778..92263fc 100644
--- a/README.org
+++ b/README.org
@@ -1,6 +1,6 @@
 #+title: Emacs setup for use with LaTeX, Org, and Python
 #+author: Gerard Vermeulen
-#+latex_class: article
+#+latex_class: article-1+2+3
 #+latex_class_options: [11pt,a4paper,english,svgnames,tables]
 #+setupfile: "setup-include.org"
 #+include: "setup-include.org"
@@ -1750,7 +1750,11 @@ this broken function (broken, since it relies on support only in org-mode before
                 ;; Reverse to go upwards to avoid wrecking the list of
                 ;; block positions in the file that would occur in case
                 ;; of going downwards.
-                (reverse blocks))))))
+                (reverse blocks)))))
+
+    ;; Push the filter on the hook.
+    (cl-pushnew #'org-latex-header-blocks-filter
+                org-export-before-parsing-hook))
 #+end_src
 
 This file uses the new way, while keeping the old way for backwards
@@ -1815,8 +1819,8 @@ the tools for the [[https://orgmode.org/][Org mode]] =kbd= macro in [[file:setup
   ,#+startup: content
 #+end_src
 
-#+caption[Define the tools of the org-mode =kbd= macro]:
-#+caption: Define the tools for the org-mode =kbd= macro.
+#+caption[Define the tools of the =Org-mode= =kbd= macro]:
+#+caption: Define the tools for the =Org-mode= =kbd= macro.
 #+name: lst:by-backend-kbd-org-macro
 #+begin_src emacs-lisp
   (with-eval-after-load 'ox
@@ -1832,15 +1836,50 @@ the tools for the [[https://orgmode.org/][Org mode]] =kbd= macro in [[file:setup
 #+end_src
 
 Listing [[lst:use-latex-header-1]], [[lst:use-latex-header-2]], [[lst:use-latex-header-3]],
-and [[lst:use-latex-header-4]] tangle into the [[file:setup-include.org][setup-include.org]] file in order to
-create the [[https://www.latex-project.org/][LaTeX]] preamble.
+[[lst:use-latex-header-4]], and [[lst:use-latex-header-5]] tangle into the
+[[file:setup-include.org][setup-include.org]] file in order to create the [[https://www.latex-project.org/][LaTeX]] preamble.
 
-#+caption[LaTeX preamble: language, lists and floats]:
-#+caption: LaTeX preamble: language, lists and floats.
+#+caption[LaTeX preamble: replacing the =Org-mode= default packages]:
+#+caption: LaTeX preamble: replacing the =Org-mode= default packages.
 #+name: lst:use-latex-header-1
 #+begin_src org
   ,#+begin_src latex-header
+    % LuaLaTeX-, PdfLaTeX-, or XeTeX-COMPILER COMPATIBILITY:
+    % Prevent collisions by using font packages before compiler specific packages.
+    \usepackage{ifthen,ifluatex,ifxetex}
+    \usepackage{amsmath}
+    \usepackage{amssymb}
+    \usepackage{pifont}          % check mark (\ding{52}) and cross mark (\ding{56})
+    \usepackage{textcomp}        % \texttimes
+    \usepackage{wasysym}         % \diameter
+    \ifthenelse{\boolean{luatex}}{
+      \usepackage{fontspec}        % lualatex
+      \usepackage{unicode-math}    % lualatex
+    }{\ifthenelse{\boolean{xetex}}{
+        \usepackage{mathspec}        % xetex
+      }{
+        \usepackage[T1]{fontenc}     % pdflatex
+        \usepackage[utf8]{inputenc}  % pdflatex
+      }
+    }
 
+    % Org-mode REQUIREMENTS:
+    \usepackage{graphicx}
+    \usepackage{longtable}
+    \usepackage{wrapfig}
+    \usepackage{rotating}
+    \usepackage[normalem]{ulem}
+    \usepackage{capt-of}
+    \usepackage{hyperref}
+
+  ,#+end_src
+#+end_src
+
+#+caption[LaTeX preamble: language, lists and floats]:
+#+caption: LaTeX preamble: language, lists and floats.
+#+name: lst:use-latex-header-2
+#+begin_src org
+  ,#+begin_src latex-header
     % LANGUAGE:
     \usepackage{babel}
     \usepackage{fvextra}
@@ -1875,7 +1914,7 @@ create the [[https://www.latex-project.org/][LaTeX]] preamble.
 
 #+caption[LaTeX preamble: page layout]:
 #+caption: LaTeX preamble: page layout.
-#+name: lst:use-latex-header-2
+#+name: lst:use-latex-header-3
 #+begin_src org
   ,#+begin_src latex-header
     % PAGE LAYOUT:
@@ -1900,7 +1939,7 @@ create the [[https://www.latex-project.org/][LaTeX]] preamble.
 
 #+caption[LaTeX preamble: float barriers]:
 #+caption: LaTeX preamble: float barriers.
-#+name: lst:use-latex-header-3
+#+name: lst:use-latex-header-4
 #+begin_src org
   ,#+begin_src latex-header
     % FLOAT BARRIERS:
@@ -1929,7 +1968,7 @@ create the [[https://www.latex-project.org/][LaTeX]] preamble.
 
 #+caption[LaTeX preamble: fancy headers and footers]:
 #+caption: LaTeX preamble: fancy headers and footers.
-#+name: lst:use-latex-header-4
+#+name: lst:use-latex-header-5
 #+begin_src org
   ,#+begin_src latex-header
     % FANCY HEADERS AND FOOTERS: