using INTERSECT and UNION in IN clause

Hi,

postgresql 7.0.2. Why by executing the following query

select * from magazine
where id in (
select mag_id from dict where word = 'akademie' intersect
select mag_id from dict where word = 'der' intersect
select mag_id from dict where word = 'klasse' )

I receive the following error:

ERROR: parse error at or near 'intersect'

while the query

select mag_id from dict where word = 'akademie' intersect
select mag_id from dict where word = 'der' intersect
select mag_id from dict where word = 'klasse' )

is executed successfully.

Is it possible to use INTERSECT and UNION keywords in subqueries?

Regards,
Alex