where K is the number of communities; L is the number of links in a network; Lk is the number of the links in the k-th community,
i.e., the two end nodes of each link are allocated to the k-th community; Dk is the sum of the degrees of nodes in the
k-th community. Such a notation is derived from assessing the differences in the expected values of the link ratios before and
after community detection.