Cluster 1
                        +------+
                       <>  R2  <>---
                      / +------+
                     /
           +------+ /   +------+
       ---<>  R1  <>---<>  R3  <>---
           +------+ \   +------+
                     \
                      \
                       \
                        \
                         \
                          \
                           \
                            \
                             \ +------+
                              <>  R10 <>---
                               +------+


       Cluster 2
           +------+     +------+
       ---<>  R2  <>---<>  R4  <>---
           +------+ \   +------+
                     \
           +------+   \ +------+
       ---<>  R3  <>---<>  R5  <>---
           +------+ \   +------+
                     \
                      \
                       \
                        \
                         \ +------+
                          <>  R9  <>---
                           +------+


       Cluster 3
                       +------+
                      <>  R6  <>---
                     / +------+
           +------+ /
       ---<>  R4  <>
           +------+ \
                     \ +------+
                      <>  R7  <>---
                       +------+


       Cluster 4
           +------+
       ---<>  R5  <>
           +------+ \
                     \ +------+
                      <>  R8  <>---
                       +------+