sentential relatives

[li202 at hermes.cam.ac.uk]

Dear All,

Does anyone know if there is a standard HPSG representation for
sentential relatives?  eg.

1. Things then improved, which surprised me.
2. Colin married my sister and I married his brother, which makes
	Colin and me double-in-laws.
3. ...which is how the Kangroo came to have a pouch.

(Quirk, et al. 1985: 1118).

If there is no standard representation, does anyone know of any
attempts to represent this kind of structure in HPSG?

I'm particularly interested in how to represent the anaphoric relation
between the relative pronoun and the preceding clause.

Thank you in advance for your help with references or suggestions.

Best,

Luli