references and inheritance

Hello

As new to postgresql :

for referencing from a table (table experiment, fk site_id) to a supertable
(table 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
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Jacques Massé
Tel. 33 (0)5 57 89 08 11 - Fax 33 (0)5 57 89 08 01