20F06 4 20F05 2 20E05 1 20F50; 20F05 1 20F67 1 Burnside group 1 Generalized triangle groups 1 Tits alternative 1 aspherisity 1 graded diagram 1 graded presentation 1 hyperbolic groups 1 intersection of groups 1 mutual commutants 1 non-isomorphic 2-generated torsion simple groups 1 normal closure of words in free groups 1 pictures 1 presentations of groups 1 small cancellation 1 small cancellation conditions 1 van Kampen diagram 1