Referencing named attribute in where clause doesn't work with 7.1.2?

Hi, this is my first post to this list so please...
I have problems getting this query to work, any ideas?

select article.title_text_key,
(select on_text.text_value from on_text whereon_text.text_key = title_text_keyAND NOT title_text_key is NULLAND
on_text.lang_id= (select code.id from code, code_group where     code.code_group_id = code_group.id      AND
code_group.description= 'lang' AND code.code_key = 'lang.NO'      ))
 
as title_text_value from article where NOT title_text_value is NULL;

ERROR:  Attribute 'title_text_value' not found

Issuing the same query without the where-clause does work tho, but
return tupples with null in them which I don't want.

--
Andreas Joseph Krogh <andreak@officenet.no>