\centerline{
\structure{\nopositioncheck\wmostaromatatom{C}\nsingle\atom{C}
\nesingle\nmostaromatatom{C}\sesingle\emostaromatatom{C}\ssingle
\atom{C}\swsingle\smostaromatatom{C}\nwsingle\phantatom{C}}
\hskip 1truecm
\structure{\nopositioncheck\atom{C}\ndouble\atom{C}\nesingle
\firstbicycloatom{C}\sesingle\atom{C}\sdouble\atom{C}\swsingle
\secondbicycloatom{C}\nwsingle\phantatom{C}}
\hskip 1truecm
\structure{\nopositioncheck\firstbicycloatom{C}\nsingle
\phantatom{C}\nesingle\secondbicycloatom{C}\swphantom
\firstbicycloatom{C}\nephantom\phantatom{C}\sesingle\atom{C}
\sdouble\atom{C}\swsingle\secondbicycloatom{C}\nwsingle
\phantatom{C}}
\hskip 1truecm
\structure{\nopositioncheck\firstbicycloatom{C}\sesingle
\phantatom{C}\nephantom\secondbicycloatom{C}\swsingle
\firstbicycloatom{C}\nephantom\phantatom{C}\nsingle\phantatom{C}
\nwsingle\secondbicycloatom{C}\sephantom\firstbicycloatom{C}
\nwphantom\phantatom{C}\swsingle\secondbicycloatom{C}\ssingle
\phantatom{C}}
}
\medskip\centerline{\bf Figure~3. \rm 
Four different benzene structures.}