graph parsetree2b { node [texmode="math",shape="none"]; S0 [label="S"]; S1 [label="S"]; S2 [label="S"]; S3 [label="S"]; S4 [label="S"]; a0 [label="a"]; a1 [label="a"]; a2 [label="a"]; S0 -- S1; S0 -- S2; S1 -- S3; S1 -- S4; S2 -- a2; S3 -- a0; S4 -- a1; }