Relational technology and concepts: theory, research systems, non-SQL implementations.
No need to suggest anything related to quasi-relational stuff like SQL here... unless it is in the guise of evaluations against the relational model itself.
Relational DataBase Management Systems (RDBMSs): working non-SQL implementations of the relational model.
The Relational Model for Database Management: the theory and corolaries behind relational databases.
No need to suggest anything related to quasi-relational stuff like SQL here... unless it is in the guise of evaluations against the relational model itself.