\begin{picture}(21,21)(2147483637,2147483637)
  \gasset{Nadjust=n}
  \gasset{Nadjust=n,Nw=1,Nh=20,Nmr=0,fillgray=0} % black rectangle
  \gasset{ExtNL=y,NLdist=3,NLangle=45} % external label right and above the node
  \gasset{Nadjust=n,Nw=20,Nh=1,Nmr=0,fillgray=0} % black rectangle
  \gasset{ExtNL=y,NLdist=3,NLangle=135} % external label right and above the node
  \gasset{Nadjust=n,Nw=1,Nh=20,Nmr=0,fillgray=0} % black rectangle
  \gasset{ExtNL=y,NLdist=3,NLangle=225} % external label right and above the node
  \gasset{Nadjust=n,Nw=20,Nh=1,Nmr=0,fillgray=0} % black rectangle
  \gasset{ExtNL=y,NLdist=3,NLangle=315} % external label right and above the node
  \gasset{ELpos=85,ELdistC=y,ELdist=0} % put (argument number) labels on the edge, toward the end
\end{picture}
