Metadata provided by CrossRef is used to create the citation trails. Only records that belong to the collections we have activated will appear in the lists of citation trails. In other words, a found record may cite more sources, but the citation trail will only show the cited sources that you'll be able to access. The same is true for later sources that cite the found record.
If citation trails are available, you will see them on the Brief Display and the Full Display.
Citing this record
Cited by this record
For some added fun, compare the "citing this record" results to Google Scholar (Cited by) and Web of Science Cited Reference search. You can use the Databases header link to get there.
Using Citation Trails (Ex Libris Knowledge Center)