if you  go to the allenbradley website http://www.ab.com/manuals/ they have
a lot of manuals (including plc) online as huge pdf files

[snip]

You might try Allen-Bradley/Rockwell Automation. Phone# listed as
1-414-382-2000, on a '95 book I have from them, called:

"MicroMentor Understanding and Applying Microprogrammable Controllers"