TY  - JOUR
AU  - Osterweil, Leon
TI  - A Theorem for Enumerating Certain Types of Collections
JO  - Canadian journal of mathematics
PY  - 1973
SP  - 74
EP  - 82
VL  - 25
IS  - 1
UR  - http://geodesic.mathdoc.fr/articles/10.4153/CJM-1973-005-8/
DO  - 10.4153/CJM-1973-005-8
ID  - 10_4153_CJM_1973_005_8
ER  -