\ProvidesPackage{nzproof}[2004/04/01]

\RequirePackage{amsmath,amssymb,amsfonts,ifthen}

\def\proofname{Proof}
\def\sketchname{Proof sketch}
\def\qedsymbol{\RIfM@\bgroup\else$\bgroup\aftergroup$\fi
  \vcenter{\hrule\hbox{\vrule\@height.6em\kern.6em\vrule}\hrule}\egroup}
\def\qed{\RIfM@\else\unskip\fi\hskip 0pt plus 1fill\hbox{}\nobreak\hskip 1 em plus 1fill\nobreak
\qedsymbol}
\newenvironment{pf}[1][]{%
\par\topsep6\p@\@plus6\p@
\trivlist \itemindent 0pt
\ifthenelse{\equal{#1}{}}%
{\item[\hskip\labelsep\sl\proofname.]\ignorespaces}%
{\item[\hskip\labelsep\sl\proofname\ (#1).]\ignorespaces}}%
{\qed\endtrivlist}
\newenvironment{ps}[1][]{%
\par\topsep6\p@\@plus6\p@
\trivlist \itemindent 0pt
\ifthenelse{\equal{#1}{}}%
{\item[\hskip\labelsep\sl\sketchname.]\ignorespaces}%
{\item[\hskip\labelsep\sl\sketchname\ (#1).]\ignorespaces}}%
{\qed\endtrivlist}

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