TY  - JOUR
AU  - G. Koester
TI  - 4-critical 4-valent planar graphs constructed with crowns.
JO  - Mathematica Scandinavica
PY  - 1990
SP  - 15
EP  - 22
VL  - 67
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/MS2_1990__67_2_167117/
ID  - MS2_1990__67_2_167117
ER  -