% Figure A.1 begins

\midinsert
\medskip

\def\facei#1{\hglue10pt\smash{\hbox to 0pt{%
\hidewidth%
\lower\fontdimen22\textfont2\hbox{$#1$}%
\hidewidth%
}}\hglue10pt}

\def\xfacei#1{\hglue20pt\smash{\hbox to 0pt{%
\hidewidth%
\lower\fontdimen22\textfont2\hbox{$#1$}%
\hidewidth%
}}\hglue20pt}

\def\htedgi#1{{\hbox to 20pt{\vrule height0.5pt depth0.5pt width0pt\hss%
\smash{\hbox to 0pt{\hidewidth%
\raise 3pt\hbox{$#1$}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height0.1pt width21.2pt depth0.1pt\hidewidth}}%
\hss}}}

\def\vtedgi#1{{\hbox to 1pt{\hss\vrule height10pt depth10pt width0pt%
\smash{\hbox to 0pt{\hidewidth%
\lower\fontdimen22\textfont2\hbox{$#1$\hglue10pt}\hidewidth}}%
\smash{\hbox to 0pt{\hidewidth%
\vrule height10.6pt width0.2pt depth10.6pt\hidewidth}}%
\hss}}}  

\centerline{
\vbox{\offinterlineskip
\hsize=20pt
\centerline{\vti{+}}
\bigskip
\centerline{\strut(a)}
}
\hskip 30pt minus 10pt
\vbox{\offinterlineskip
\setbox0=\hbox{\vti{-}\xfacei{}\vti{+}\xfacei{}\vt}
\hsize=\wd0
\box0
\hbox{\chdown \xfacei{=}\chup \xfacei{=}\vtedgi{+}}
\hbox{\vti{+}\xfacei{}\vti{-}\xfacei{}\vt}
\smallskip
\centerline{\strut(b)}
}
\hskip 30pt minus 10pt
\vbox{\offinterlineskip
\hsize=20pt
\setbox0=\hbox{\vti{-}\htedg\vti{+}\xfacei{}\vti{+}\htedg\vti{-}}
\hsize=\wd0
\box0
\hbox{\vtedg\facei{\hookrightarrow}\vtedg\xfacei{=}%
\vtedg\facei{\hookleftarrow}\vtedg}
\hbox{\vti{+}\htedg\vti{-}\xfacei{}\vti{-}\htedg\vti{+}}
\smallskip
\centerline{\strut(c)}
}
}
\vskip 15pt
\centerline{
\vbox{\offinterlineskip
\hsize=20pt
\setbox0=\hbox{\vt\xfacei{}\vti{+}}
\hsize=\wd0
\box0
\hbox{\vtedgi{+}\xfacei{\mapsto}\pvt}
\hbox{\vt\xfacei{}\vti{+}}
\smallskip
\centerline{\strut(d)}
}
\hskip 30pt minus 10pt
\vbox{\offinterlineskip
\hsize=20pt
\setbox0=\hbox{\vti{-}\htedg\vti{+}\xfacei{}\vt\htedgi{-}\vt}
\hsize=\wd0
\box0
\hbox{\vtedg\facei{\hookrightarrow}\vtedg\xfacei{\mapsto}%
\vtedgi{+}\phe\vtedgi{+}}
\hbox{\vti{+}\htedg\vti{-}\xfacei{}\vt\htedgi{-}\vt}
\smallskip
\centerline{\strut(e)}
}
}

\nobreak
\smallskip
\nobreak

\centerline{\bf Figure A.1}

\smallskip
\endinsert

% Figure A.1 ends
