TY  - JOUR
AU  - Pfeffer, W. F.
TI  - On the Lower Derivate of a Set Function
JO  - Canadian journal of mathematics
PY  - 1968
SP  - 1489
EP  - 1498
VL  - 20
IS  - 1
UR  - http://geodesic.mathdoc.fr/articles/10.4153/CJM-1968-149-8/
DO  - 10.4153/CJM-1968-149-8
ID  - 10_4153_CJM_1968_149_8
ER  -