%%
%% The LaTeX Companion, 2ed (second printing August 2004)
%%
%% Example 8-2-25 on page 482.
%%
%% 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{207.0pt}

\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
\begin{align}
  x^2+y^2 &= z^2 \label{eq:A}            \\
  x^3+y^3 &= z^3 \notag                  \\
  x^4+y^4 &= r^4 \tag{$*$}               \\
  x^5+y^5 &= r^5 \tag*{$*$}              \\
  x^6+y^6 &= r^6 \tag{\ref{eq:A}$'$}     \\
      A_1 &= N_0 (\lambda ; \Omega')
             - \phi ( \lambda ; \Omega') \\
      A_2 &= \phi (\lambda ; \Omega')
             \, \phi (\lambda ; \Omega)
             \tag*{ALSO (\theequation)}  \\
      A_3 &= \mathcal{N} (\lambda ; \omega)
\end{align}
\end{document}