textwp60.zip, texttext.zip, and textps.zip are three different versions
of the same file.  

The document contained in each of the files is a self-explanatory description
of 3 approaches to real-time texture mapping such as that done in DOOM.

textwp60 -- WordPerfect 6.0 format
texttext -- ASCII text format
textps   -- PostScript format

There are illustrations in the WP and PS docs which were not includable in
the ASCII version.  I strongly suggest getting one of these two formats
if possible.  The graphics lend a lot to the text.