The Third Manifesto
This is a proposal for a strictly relational system. It is intended to be more powerful than SQL or object DBMSs. File in PostScript format.

Database Debunkings
Analysis of various systems and ideas floating in the database scene, against the standards set by the relational model for database management.

Against the Grain
Contrarian articles by Fabian Pascal about the necessity of getting the relational model properly implemented.

FirstSQL Issue Papers
Opinions fundamented on the relational model about NULLs, SQL and DBMS

Dilip's Brief Introduction to Relational Databases
Provides a basic introduction to relational databases theory.

Dr EF "Ted" Codd's 12 Rules
12 rules for a relational database management system, by the relational model's author. Outdated but still useful.

Extending the Database Relational Model to Capture More Meaning
RM/T: semantics modeling in the relational model for database management.

According to Date: recent.
Articles by Christohper J Date with emphasis on foundations. Web published by DBPD after the print magazine folded.

According to Date: online.
Articles by Christopher J Date about how the relational model can fulfill all OO needs. Web-only articles from DBPD that never made to print.

Introduction to Relational Databases
Concentrating on the 12 Rules from EF Codd and a succint, informal definition of normalisation with examples.

Chracteristics of a Relational Database
Succint, itemized explanation of 12 Rules by EF Codd.

Normalization
The five normal forms succintly, informally described.

12 Rules
12 Rules for a relational database by EF Codd.

The Third Manifesto
Additional material related to the book.

eAI Journal - Data Integration Department
Containing several short, insightful articles by David McGoveran on the relevance of the Relational Model to enterprise application integration.

A Relational Model of Data for Large Shared Data Banks
The paper that started it all. The first public statement of the Relational Model.

A Simple Guide to Five Normal Forms
A Simple Guide to Five Normal Forms in Relational Database Theory

Fondation Matters
Series of relational database model articles by Chris J Date, with emphasis on rules applications. Registration required.

Tuple-Marks
A proposal to avoid default or special values, SQL NULLs and three-valued logic in the representation of missing information.