G7
        |\
     ---|-\----------O-------------------------------------------
        |  >                                                     
     ---|-/----------O-------------------------------------------
        |/                                                       
     ---/------------O-------------------------------------------
       /|  _                                                     
     -<-|-<->--------O-------------------------------------------
       \|  /                                                     
     ---|\/------------------------------------------------------
        |                                                        
        V


Figure 5.2