TY  - JOUR
AU  - Yu. A. Ignatov
TI  - Free and nonfree subgroups of $PSL_2(\mathbf C)$ generated by two parabolic elements
JO  - Sbornik. Mathematics
PY  - 1979
SP  - 49
EP  - 55
VL  - 35
IS  - 1
UR  - http://geodesic.mathdoc.fr/item/SM_1979_35_1_a3/
LA  - en
ID  - SM_1979_35_1_a3
ER  -