references and inheritance

Hello

As new to postgresql :

for referencing from a table (experiment, fk site_id) to a supertable (site
pk site_id)
 inherited by some site_type1, site_type2, ...

is it better to reference each of them or to use  the method given by Jon
Obuchowski in the interactive doc for PostgreSQL (Chapter 8 - Inheritance) ?

Thanks
___________________________________________
Jacques Massé
Tel. 33 (0)5 57 89 08 11 - Fax 33 (0)5 57 89 08 01