is mentioned by

Def tTop == tree_leaf(inr())	[st_top]
Def t == tree_leaf(inl(t))	[typ]
Def f == tree_leaf(ts_op(f))	[topr]
Def l' == tree_leaf(ts_pvar(l))	[tpvar]
Def trace(l) == tree_leaf(ts_trace(l))	[ttrace]
Def l == tree_leaf(ts_fvar(l))	[tfvar]
Def l == tree_leaf(ts_var(l))	[tvar]

In prior sections: mb tree

Try larger context: GenAutomata