TY  - JOUR
AU  - Gordana M. Pavlović
TI  - On the Operations Over Relations in the Relational Model of Data with two Types of Null Values
JO  - Publications de l'Institut Mathématique
PY  - 1983
SP  - 151 
VL  - _N_S_34
IS  - 48
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/PIM_1983_N_S_34_48_a23/
LA  - en
ID  - PIM_1983_N_S_34_48_a23
ER  -