Before revision:  In the following section we describe in detail sections 4.2 (Cluster collection) and 5 (Data Structure and Space Complexity) in \mbox{%DIFAUXCMD paolaSiam to show the implementation of the data structure.
After revision:  In the following section we describe in detail sections 4.2 (Cluster collection) and 5 (Data Structure and Space Complexity) in 3 to show the implementation of the data structure.