Google and Amazon have each made citations more visible in recent weeks. It has been widely noted that Google Scholar will often disappoint users by providing a [citation] entry that does not resolve to an actual document. Less remarked is the very welcome ability to be able to follow a cited by link. Citation also appears to be an important part of the ranking algorithm employed.
Amazon has also introduced a citation feature.
Amazon.com Citations is a program that helps customers discover books related to the ones they're interested in. Amazon scans every book in the Search Inside the Book� program looking for phrases that match the names of books in our catalog. We make a note of these "citations" and display them to you in one of two ways.For an example see the list of cited works included in the details for Dependent rational animals. Where it has data, Amazon also includes a cited by list. See the list of books, including the one above, which cite Playing and reality. Such forward and backward linking is very helpful.
- If a book cites two other books, we show you which two books it cites, and link to the pages in the book where the citations appear.
- If a book is cited by two other books, we show you which two books cite it, and link to the pages in those books where the citations appear.
In each case, issues of authority control are also highlighted. For example, Amazon notes that one reason that results may not be comprehensive is that there may not be a match between author names in citations and author names in their catalog.