TY  - JOUR
AU  - K. Krzyżewski
TI  - Note on approximative derivative
JO  - Colloquium Mathematicum
PY  - 1963
SP  - 281
EP  - 285
VL  - 10
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.4064/cm-10-2-281-285/
DO  - 10.4064/cm-10-2-281-285
LA  - en
ID  - 10_4064_cm_10_2_281_285
ER  -