%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-4-40 on page II-179 in "Extra decorations for symbols".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3examargin}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{135.0pt}

  % Shorten the vertical size of the example ...
  \AtBeginDocument{%
    \setlength\abovedisplayskip{.5\abovedisplayskip}%
    \setlength\belowdisplayskip{.5\belowdisplayskip}%
  }

%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands

\begin{document}
\[ \overset{*}{X} > \underset{*}{X}
   \overunderset{\mathsf{def}}{\mathsf{loc.}}{\iff}
   \sideset{}{'}\sum_{a,b \in \mathbf{R^*}}
                       \overset{a}{\underset{b}{X}} = X \]
\end{document}