TY  - BOOK
AU  - Codd,E.F.
TI  - The relational model for database management: version 2 
SN  - 0-201-14192-2
AV  - QA76.9 .D3 C63
PY  - 1990///
CY  - Reading, Mass.
PB  - Addison-Wesley
N1  - Bibliografia:  p. 505-510
ER  -