TY  - JOUR
AU  - McAdam, Stephen
TI  - Going Down and Open Extensions
JO  - Canadian journal of mathematics
PY  - 1975
SP  - 111
EP  - 114
VL  - 27
IS  - 1
UR  - http://geodesic.mathdoc.fr/articles/10.4153/CJM-1975-013-5/
DO  - 10.4153/CJM-1975-013-5
ID  - 10_4153_CJM_1975_013_5
ER  -