Referencing Serial Type as Foreign Key

Don't know why I've not come across this before, but I have now.

In a table definition I reference the primary key of another table. That
key is of datatype SERIAL. In the referencing table, do I define the column
as

col_name INTEGER REFERENCES other-table (primary_key_field),

or is the datatype SERIAL because that's what the referenced
primary_key_field is?

Thanks,

Rich

--
Dr. Richard B. Shepard, President
Applied Ecosystem Services, Inc. (TM)
<http://www.appl-ecosys.com> Voice: 503-667-4517 Fax: 503-667-8863