The titles are similar, but they represent snapshots in time, and the contents of the most recent of the papers is probably most useful. In particular, the SPIE paper is most up to date and more implementation-related. A 1997 paper by senior Martin Proulx, on his experiments in parsing of mathematics. He found it better to follow center-lines rather than baselines. His results are summarized in A Solution to Mathematics Parsing.
Related programs are available on request.
Here is a draft of a paper on how to separate mathematical material from text in a document, How to Find Mathematics on a Scanned Page. Eventually, a long paper on the details of the lisp programs will appear. Unless you are really interested in doing stuff in Lisp and have an urgent need to use this, maybe you should wait.