\pagestyle{headings}
\parindent=0mm
\input amssym.def
\input amssym.tex
\newtheorem{thr}{Theorem}

\def\N{{\Bbb N}}
\def\Z{{\Bbb Z}}
\def\R{{\Bbb R}}
%
% macros pour les diagrammes rectangulaires
%
\def\hfl#1#2{\smash{\mathop{\hbox to 15mm{\rightarrowfill}}
\limits^{\scriptstyle#1}_{\scriptstyle#2}}}
%
\def\hflr#1#2{\smash{\mathop{\hbox to 15mm{\rightarrowfill}}
\limits^{\scriptstyle#1}_{\scriptstyle#2}}}
%
\def\hfll#1#2{\smash{\mathop{\hbox to 15mm{\leftarrowfill}}
\limits^{\scriptstyle#1}_{\scriptstyle#2}}}
%
\def\vfl#1#2{\llap{$\scriptstyle #1$}\left\downarrow
\vbox to 7mm{}\right.\rlap{$\scriptstyle #2$}}
%
\def\vflu#1#2{\llap{$\scriptstyle #1$}\left\uparrow
\vbox to 7mm{}\right.\rlap{$\scriptstyle #2$}}
%
\def\diagram#1{\def\normalbaselines{\baselineskip=0pt
\lineskip=10pt\lineskiplimit=1pt} \matrix{#1}}
%
% macro tvi pour les lignes verticales et horizontales dans un tableau
%
\def\tvi{\vrule height 12pt depth 5pt width 0pt}
\def\tv{\tvi\vrule}