<citerefentry>
  <refentrytitle>intro</refentrytitle>
  <manvolnum>2</manvolnum>
</citerefentry>
describes the surroundings of system calls and contains a list
of available man-pages. An additional look into directory 
<filename>/usr/share/man/sman2</filename> can't hurt, though.
A general purpose interface to system calls is described by
<citerefentry>
  <refentrytitle>syscall</refentrytitle>
  <manvolnum>2</manvolnum>
</citerefentry>.
Anyway, the statement <literal>&xml.magic.revealed.syscall.asm;</literal>
corresponds to the value of <literal>SYS_write</literal> in
<filename>/usr/include/sys/syscall.h</filename>.
