The three disks are similar in that they each have the works of the
author concerned on them.  The search engines for texts is excellent.
That is, they function as well as a concordance and quickly.

Are the disks perfect?  No.  Is concordance access to the works of Twain,
Shakespeare and Dickens worth the less than $17 each costs?  For me, yes.

I give the information only because people on the list keep requesting
information which is easily come by with this concordance facility and is
almost impossible to come by otherwise.

U. S. Naval Academy