%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-4-6 on page II-166 in "Fractions and their generalizations".
%%
%% 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{351.0pt}

  % Shorten the vertical size of the example ...
  \AtBeginDocument{%
    \setlength\abovedisplayskip{.1\abovedisplayskip}%
    \setlength\belowdisplayskip{.3\belowdisplayskip}%
  }

%StartShownPreambleCommands
\usepackage{mathtools}
%StopShownPreambleCommands

\begin{document}
\[ A =    \frac{\splitfrac{a + b + c + d}{ + e + f + \sum_i x_i}}{\alpha}
   \simeq \frac{\splitdfrac{a + b + c + d}{ + e + f + \sum_i x_i}}{\beta}
     <    \frac{\omega}{\splitfrac{z - y - x - w - v - u}
                                  {\splitfrac{\mathstrut - t - s - r - q}
                                             { - p - o - n - m}}}      \]
\end{document}