Latex for CG

[Ash Asudeh]

*Apologies for multiple copies*

Does anyone know of latex macros for creating CG derivation trees with
string at top, tree growing downward (as in e.g. Steedman's work,
Carpenter's TLS book)? I've searched on the web fairly hard, but
surprisingly: nothing.

I've tried to use Taylor's prooftree.sty, but I haven't been able to get
it to behave in the desired way.

Thanks,
Ash