% Figure 4.4 begins

\midinsert
\medskip

\centerline{
\vbox{\offinterlineskip
\setbox0=\hbox{\vti{0} \hedg \vti{1} \hedg \vti{0} \hedg \vti{1}}
\hsize=\wd0
\box0
\hbox{\vtedg \phe \vtedg \phe \vtedg \phe \vtedg}
\hbox{\vti{-1} \phe \vti{2} \phe \vti{-1} \phe \vti{2}}
\hbox{\vtedg \phe \vtedg \phe \vtedg \phe \vtedg}
\hbox{\vti{0} \hedg \vti{1} \hedg \vti{0} \hedg \vti{1}}
\smallskip
\centerline{\strut(a)}
}
\hskip 30pt minus 10pt
\vbox{\offinterlineskip
\setbox0=\hbox{\vti{-2} \hedg \vti{-1} \hedg \vti{-2} \hedg \vti{-1}}
\hsize=\wd0
\box0
\hbox{\vtedg \phe \vtedg \phe \vtedg \phe \vtedg}
\hbox{\vti{-3} \phe \vti{0} \phe \vti{-3} \phe \vti{0}}
\hbox{\vtedg \phe \vtedg \phe \vtedg \phe \vtedg}
\hbox{\vti{-2} \hedg \vti{-1} \hedg \vti{-2} \hedg \vti{-1}}
\smallskip
\centerline{\strut(b)}
}
}

\nobreak
\bigskip
\nobreak

\centerline{
\vbox{\offinterlineskip
\setbox0=\hbox{\vti{4} \hedg \vti{5} \hedg \vti{4} \hedg \vti{5}}
\hsize=\wd0
\box0
\hbox{\vtedg \phe \pvt \phe \vtedg \phe \pvt}
\hbox{\vti{3} \htedg \vti{2} \htedg \vti{3} \htedg \vti{2}}
\hbox{\pvt \phe \vtedg \phe \pvt \phe \vtedg}
\hbox{\vti{0} \hedg \vti{1} \hedg \vti{0} \hedg \vti{1}}
\smallskip
\centerline{\strut(c)}
}
\hskip 30pt minus 10pt
\vbox{\offinterlineskip
\setbox0=\hbox{\vti{0} \hedg \vti{1} \hedg \vti{0} \hedg \vti{1}}
\hsize=\wd0
\box0
\hbox{\vtedg \phe \pvt \phe \vtedg \phe \pvt}
\hbox{\vti{-1} \htedg \vti{-2} \htedg \vti{-1} \htedg \vti{-2}}
\hbox{\pvt \phe \vtedg \phe \pvt \phe \vtedg}
\hbox{\vti{-4} \hedg \vti{-3} \hedg \vti{-4} \hedg \vti{-3}}
\smallskip
\centerline{\strut(d)}
}
}

\nobreak
\smallskip
\nobreak

\centerline{\bf Figure 4.4}

\smallskip
\endinsert

% Figure 4.4 ends
