I can't help you with those particular papers/books but I can point you at modern equivalents.
These guys (Chris Date, Fabian Pascal, Hugh Darwen) are well known for their theory and practical sense in the DBMS world. I would imagine their very names strike fear into the likes of Oracle, IBM and Microsoft :-)
A lot of their work is grounded in Codd's principles, but they have also moved forwards into a much more modern world.
I would recommend "Practical Issues in Database Management" and "Foundations for future database systems - the third manifesto".
You can find the authors regularly hanging out on www.dbdebunk.com. Initially they can appear to be rather aloof, but bear with them and you'll come to understand why. Send an email to Fabian, tell him what you're hoping to read and understand and he'll point you at a suitable paper/book etc. But for god's sake don't argue de-normalisation with him or you will bleed :-)
In my humble opinion, these guys are simply the most well versed, up to date, practical and theoretical people in this field. They're also *very* widely published.