There are tons of free text analysis/data mining tools available. While most are concordance tools, there are some which provide linking features. Here is one site that reviews much of what is available by category: Text Analysis Info.
You may also search for Plagiarism Tools. Some of these are free, such as CopyFind v2.6 which you can directly find with Google.
Also, if you do the search: text analysis software free, there is enough to keep you busy for a long time.
For building a web bibliography of what’s available, enter the same search in the Ultimate Research Assistant (Ultimate Research Assistant (Web Edition)) and you will get a very complete listing of available text tools.
You may also want to remove the FREE from either/both of your searches, giving you a much wider selection of what’s out there. If I can be of further assistance, please let me know, via a private email or message.
As a now retired statistician, I have been heavily involved in developing text analysis tools, and will be happy to share some of my experience with you.