You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: The Forwarding Indices of Graphs -- a Survey 
Chapter Title:  Forwarding Indices of Some Graphs 
1. Abstract of Cited Paper (BIB001):  For a given connected graph $G$ of order $n$, a routing $R$ is a set of $n(n-1)$ elementary paths specified for every ordered pair of vertices in $G$. The vertex-forwarding index $\xi(G)$ (the edge-forwarding index $\pi(G)$) of $G$ is the maximum number of paths of $R$ passing through any vertex (resp. edge) in $G$. In this paper we consider the vertex- and the edge- forwarding indices of the cartesian product of $k\,(\ge 2)$ graphs. As applications of our results, we determine the vertex- and the edge- forwarding indices of some well-known graphs, such as the $n$-dimensional generalized hypercube, the undirected toroidal graph, the directed toroidal graph and the cartesian product of the Petersen graphs.

Literature Review:
The forwarding indices of some very particular graphs have been determined. We list all main results that we are interested in and have known, all of which not noted can be found in Heydemann et at  or determined easily. 1. For a complete graph K n , ξ(K n ) = 0 and π(K n ) = 2. 2. For a star K 1, n−1 , ξ(K 1, n−1 ) = (n − 1)(n − 2) and π(K 1, n−1 ) = 2(n − 1). 3. For a path P n , ξ(P n ) = 2  In particular, 4, for n = 2; 5, for n = 3, 4; 6, for n ≥ 5; 6. The n-dimensional undirected toroidal mesh In particular, The last result was obtained by Heydemann et al  . In particular, 8. The n-dimensional generalized hypercube, denoted by Q(d 1 , d 2 , · · · , d n ), where d i ≥ 2 is an integer for each i = 1, 2, · · · , n, is defined as the cartesian products ) is called the d-ary n-dimensional cube, denoted by Q n (d). It is clear that Q n (2) is Q n . Xu et al BIB002 determined that For the n-dimensional hypercube Q n , ξ(Q n ) = (n − 2)2 n−1 + 1 and π(Q n ) = 2 n . The last result was obtained by Heydemann et al  . 9. For the crossed cube CQ n (n ≥ 2), π(CQ n ) = π m (CQ n ) = 2 n decided by Chang et al BIB001 . However, ξ(CQ n ) has not been determined so far.