Local search is mentioned in Hummon and Doreian<ref name=":0" /> as "priority first" search. This search process always chooses the next link(s) with the highest SPX as the outgoing link. It keeps tracking the most traversed link(s) thus obtains the main stream among all citation chains. Figure 4 shows the local main paths that are obtained based on SPC. Noticing that when the search reaches the node I, two outgoing links have the same SPC values thus producing two paths afterwardsafterward.
[[File:Local key-route main paths SPC.png|thumb|Figure 6. Local key-route main paths in a sample citation network]]
==== Global search ====
Global search simply suggestsuggests the citation chain with the largest overall SPX. The concept of global search is similar to the [[critical path method]] in project scheduling. The global main paths of the sample citation network based on SPC is presented in Figure 5. The sum of all the SPC values in the path B-D-F-I-M-N is 15, which is the largest among all possible paths.
[[File:Global key-route main paths SPC.png|thumb|Figure 7. Global key-route main paths in a sample citation network]]
==== Key-route search ====
Key-route search is designed to avoid the problem of missing significant links in both the local and global search. The problem is in the local and global main paths shown above, in which one of the most important linklinks (H, K) is not included in the main paths. As described in Liu and Lu (2012)<ref name=":1" />, the approach searches main paths from the specified links (key-routes) thus guarantees the inclusion of the links. One can also specify multiple links to obtain multiple main paths. An additional advantage of the key-route approach is that one is able to control the detail of the main paths by varying the number of key-routes. The larger the number of key-route is specified, the more detail is revealsrevealed. When the number of key-route increases to a certain point the search returns the whole citation network. Figure 6 and 7 show the local key-route and global key-route main paths of the sample citation network. In both main paths the number of key-route is set to 1, i.e., doing the search base on only the top links. Since there are two top links (B, D) and (H, K), the resulting main paths include both of them.
