TY  - JOUR
AU  - Eric Mendelsohn
TI  - An Elementary Characterization of the Category of (Free) Relational Systems.
JO  - Mathematische Zeitschrift
PY  - 1970
SP  - 224
EP  - 232
VL  - 113
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MZ_1970__113_171271/
ID  - MZ_1970__113_171271
ER  -