Sekcja LaTeX2e zawierająca definicje polecenia `startsection`

    \newcount\@secpenalty%
    \@secpenalty = -300%
    \newif\if@noskipsec%
    \@noskipsectrue%
    %
    \def\@startsection#1#2#3#4#5#6{%
       \if@noskipsec%
           \leavevmode%
       \fi%
       \par%
       \@tempskipa #4\relax%
       \@afterindenttrue%
       \ifdim \@tempskipa < \z@%
           \@tempskipa -\@tempskipa%
           \@afterindentfalse%
       \fi%
       \if@nobreak%
           \everypar{}%
        \else%
           \addpenalty\@secpenalty%
           \addvspace\@tempskipa%
       \fi%
       \@ifstar%
           {\@ssect{#3}{#4}{#5}{#6}}%
           {\@dblarg{\@sect{#1}{#2}{#3}{#4}{#5}{#6}}}}%
    %
    %
    \def\@sect#1#2#3#4#5#6[#7]#8{%
         \ifnum #2> \c@secnumdepth%
             \let\@svsec\@empty%
          \else%
             \refstepcounter{#1}%
             \protected@edef\@svsec{\@seccntformat{#1}\relax}%
         \fi%
         \@tempskipa #5\relax%
         \ifdim \@tempskipa > \z@%
             \begingroup
                 #6\relax%
                 \@hangfrom{\hskip #3\relax\@svsec}%
                 {\interlinepenalty \@M #8\par}%
            \endgroup%
           \csname #1mark\endcsname{#7}%
           \addcontentsline{toc}{#1}{%
                             \ifnum #2>\c@secnumdepth%
                              \else%
                                  \protect\numberline{\csname the#1\endcsname}%
                             \fi%
                             #7}%
         \else%
            \def\@svsechd{#6%
                          \hskip #3\relax  %% \relax added 2 May 90
                          \@svsec #8\csname #1mark\endcsname%
                          {#7}%
                          \addcontentsline{toc}{#1}{%
                                  \ifnum #2>\c@secnumdepth%
                                   \else%
                                      \protect\numberline{\csname the#1\endcsname}%
                                  \fi%
                                  #7}}%
        \fi%
        \@xsect{#5}}%
    %
    \def\@xsect#1{%
        \@tempskipa #1\relax%
        \ifdim \@tempskipa>\z@%
            \par \nobreak%
            \vskip \@tempskipa%
            \@afterheading%
         \else%
            \global\@nobreakfalse%
            \global\@noskipsectrue%
            \everypar{\if@noskipsec%
                          \global\@noskipsecfalse%
                          \clubpenalty\@M%
                          \hskip -\parindent%
                          \begingroup
                              \@svsechd
                          \endgroup%
                          \unskip%
                          \@tempskipa #1\relax%
                          \hskip -\@tempskipa%
                       \else%
                          \clubpenalty \@clubpenalty%
                          \everypar{}%
                      \fi}%
        \fi%
        \ignorespaces}%
    %
    \def\@seccntformat#1{%
        \csname the#1\endcsname%
        \quad}%
    %
    \def\@ssect#1#2#3#4#5{%
        \@tempskipa #3\relax%
        \ifdim \@tempskipa > \z@%
            \begingroup%
                #4%
                \@hangfrom{\hskip #1}%
                {\interlinepenalty \@M #5\par}%
            \endgroup%
        \else%
           \def\@svsechd{#4\hskip #1\relax #5}%
       \fi%
       \@xsect{#3}}%
    %
    \newif\if@afterindent%
    \@afterindenttrue%
    %
    \def\@afterheading{%
        \global\@nobreaktrue%
        \everypar{\if@nobreak%
                      \global\@nobreakfalse%
                      \clubpenalty \@M%
                      \if@afterindent%
                       \else%
                          {\setbox\z@\lastbox}%
                      \fi%
                   \else%
                      \clubpenalty \@clubpenalty%
                      \everypar{}%
                  \fi}}%
    %
    \def\@hangfrom#1{%
        \setbox\@tempboxa\hbox{{#1}}%
        \hangindent \wd\@tempboxa%
        \noindent\box\@tempboxa}%
    %
    %
    \newcount\c@secnumdepth%
    \newcount\c@tocdepth%
    %
    \def\secdef#1#2{\@ifstar{#2}{\@dblarg{#1}}}%
    %
    \def\sectionmark#1{}%
    \def\subsectionmark#1{}%
    \def\subsubsectionmark#1{}%
    \def\paragraphmark#1{}%
    \def\subparagraphmark#1{}%