%%
%% The LaTeX Companion, 2ed (second printing August 2004)
%%
%% Example 8-5-3 on page 497.
%%
%% Copyright (C) 2004 Frank Mittelbach, Michel Goossens,
%%    Johannes Braams, David Carlisle, and Chris Rowley
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3
%% of this license or (at your option) any later version.
%%
%% See http://www.latex-project.org/lppl.txt for details.
%%

\documentclass{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{183.0pt}

\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
\begin{align*}
\widehat        {\psi_\delta(t) E_t h}
&= \widetilde   {\psi_\delta(t) E_t h}    \\
\overline       {\psi_\delta(t) E_t h}
&= \underline   {\psi_\delta(t) E_t h}    \\
\overbrace      {\psi_\delta(t) E_t h}
&= \underbrace  {\psi_\delta(t) E_t h}
& & \text{Do not change style}            \\
\overrightarrow {\psi_\delta(t) E_t h}
&= \overleftarrow {\psi_\delta(t) E_t h}
& &   \text{Do not change style}     \\[-3pt]
& & & \text{without \textsf{amsmath}}     \\
\underrightarrow  {\psi_\delta(t) E_t h}
&= \underleftarrow  {\psi_\delta(t) E_t h}
& & \text{Do need \textsf{amsmath}}       \\
\overleftrightarrow {\psi_\delta(t) E_t h}
&=\underleftrightarrow{\psi_\delta(t) E_t h}
& & \text{Do need \textsf{amsmath}}
\end{align*}
\end{document}
