diff --git a/quad8/continuummechanics/notes/preamble.tex b/quad8/continuummechanics/notes/preamble.tex
new file mode 100644
index 0000000..e4f99ee
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+++ b/quad8/continuummechanics/notes/preamble.tex
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+\usepackage{physics} % For the \laplacian command
+
+\setlength{\parskip}{1em}
+
+% Plantilles del notate
+\def\myupbracefill#1{\rotatebox{90}{\stretchto{\{}{#1}}}
+\def\rlwd{.5pt}
+\newcommand\notate[4][B]{%
+  \if B#1\else\def\myupbracefill##1{}\fi%
+  \def\useanchorwidth{T}%
+  \setbox0=\hbox{$\displaystyle#2$}%
+  \def\stackalignment{c}\stackunder[-6pt]{%
+    \def\stackalignment{c}\stackunder[-1.5pt]{%
+      \stackunder[2pt]{\strut $\displaystyle#2$}{\myupbracefill{\wd0}}}{%
+    \rule{\rlwd}{#3\baselineskip}}}{%
+  \strut\kern9pt$\rightarrow$\smash{\rlap{$~#4$}}}%
+}
+
+% Tensor commands:
+\newcommand*{\TT}[1]{\bar{\bar{#1}}}