TY  - JOUR
AU  - Havel, Václav
TI  - Universality property of free groupoid extensions of halfgroupoids and its geometrical meaning
JO  - Czechoslovak Mathematical Journal
PY  - 1975
SP  - 562
EP  - 567
VL  - 25
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1975.101352/
DO  - 10.21136/CMJ.1975.101352
LA  - en
ID  - 10_21136_CMJ_1975_101352
ER  -