3 files changed, 36 insertions, 11 deletions
diff --git a/content/latexHeaders/code.sty b/content/latexHeaders/code.sty
index 3ebdda3..8a600c5 100644
--- a/content/latexHeaders/code.sty
+++ b/content/latexHeaders/code.sty
@@ -1,3 +1,6 @@
+\usepackage{ocgx2}
+\usepackage{fontawesome}
+
 % Colors, used for syntax highlighting.
 % To print this document, set all colors to black!
 \usepackage{xcolor}
@@ -101,6 +104,32 @@
 %	\addtocounter{lstnumber}{-1}%
 %}
 
+\ifthenelse{\isundefined{\srclink}}{}{
+	\lst@AddToHook{Init}{%
+		\ifthenelse{\equal{\lst@name}{}}{}{%
+			\begin{minipage}[t][0pt]{\linewidth}%
+				\vspace{0pt}%
+				\hfill%
+				\begin{ocg}[printocg=never]{Source links}{srclinks}{1}%
+					\hfill\href{\srclink{\lst@name}}{\faExternalLink}%
+				\end{ocg}%
+			\end{minipage}%
+		}%
+	}
+}
+
+\lst@AddToHook{DeInit}{%
+	\ifthenelse{\equal{\lst@name}{}}{}{%
+		\begin{minipage}[b][0pt]{\linewidth}%
+			\vspace{0pt}%
+			\hfill%
+			\begin{ocg}[printocg=never]{Source file names}{srcfiles}{0}%
+				\hfill\textcolor{gray}{\lst@name}%
+			\end{ocg}%
+		\end{minipage}%
+	}%
+}
+
 \newenvironment{btHighlight}[1][]
 {\begingroup\tikzset{bt@Highlight@par/.style={#1}}\begin{lrbox}{\@tempboxa}}
 {\end{lrbox}\bt@HL@box[bt@Highlight@par]{\@tempboxa}\endgroup}
diff --git a/content/latexHeaders/commands.sty b/content/latexHeaders/commands.sty
index edbba1b..73a7dca 100644
--- a/content/latexHeaders/commands.sty
+++ b/content/latexHeaders/commands.sty
@@ -7,6 +7,11 @@
 \newcommand{\code}[1]{\lstinline[breaklines=true]{#1}}
 \let\codeSafe\lstinline
 
+\ifoptional
+	\renewcommand{\columnbreak}{}
+	\newcommand\opthint{\textcolor{gray}{(optional)}}
+\fi
+
 \usepackage{tikz}
 \usetikzlibrary{angles,quotes}
 
@@ -17,7 +22,7 @@
 	\ifthenelse{\equal{#1}{optional}}{%
 		\optional{
 				\needspace{4\baselineskip}%
-				\subsection{#2\textcolor{gray}{(optional)}}%
+				\subsection{#2 \opthint}%
 				#3%
 			}
 	}{%
diff --git a/content/latexHeaders/math.sty b/content/latexHeaders/math.sty
index d758f71..8219782 100644
--- a/content/latexHeaders/math.sty
+++ b/content/latexHeaders/math.sty
@@ -41,7 +41,7 @@
   \end{matrix}
   \Bigr)
 }
-% Euler numbers, first kind.
+% Eulerien numbers, first order.
 \newcommand{\eulerI}[2]{
   \Bigl\langle
   \begin{matrix}
@@ -50,15 +50,6 @@
   \end{matrix}
   \Bigr\rangle
 }
-% Euler numbers, second kind.
-\newcommand{\eulerII}[2]{
-  \Bigl\langle\mkern-4mu\Bigl\langle
-  \begin{matrix}
-    #1 \\
-    #2
-  \end{matrix}
-  \Bigr\rangle\mkern-4mu\Bigr\rangle
-}
 % Stirling numbers, first kind.
 \newcommand{\stirlingI}[2]{
   \Bigl[