TY  - JOUR
AU  - Lee, S. J.
TI  - Perturbation of Direct Sum Differential Operators
JO  - Canadian journal of mathematics
PY  - 1978
SP  - 600
EP  - 630
VL  - 30
IS  - 3
UR  - http://geodesic.mathdoc.fr/articles/10.4153/CJM-1978-053-7/
DO  - 10.4153/CJM-1978-053-7
ID  - 10_4153_CJM_1978_053_7
ER  -