TY  - JOUR
AU  - El-sayed Ibrahim, Sobhy
TI  - The General Differential Operators Generated by a Quasi-Differential Expressions with their Interior Singular Points
JO  - Serdica Mathematical Journal
PY  - 1999
SP  - 207
EP  - 240
VL  - 25
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SMJ2_1999_25_3_a2/
LA  - en
ID  - SMJ2_1999_25_3_a2
ER  -