case, new column not found

I'm trying somethings here and I get strange errors:

select *,((CASE WHEN titulo LIKE '%Matematica%' THEN 1 ELSE 0 END) + (CASE WHEN descripcion LIKE '%Matematica%' THEN 1 ELSE 0 END) +(CASE WHEN incumbencia LIKE '%Matematica%' THEN 1 ELSE 0 END) ) 
AS encontrados 
FROM admin_view 
WHERE admin_view.nivel=1 AND encontrados > 0;

ERROR:  Attribute 'encontrados' not found

Why is it? encontrados should be an attribute of type INT with the count of 
the rows found.

Any ideas?

Saludos... :-)

-- 
Cualquiera administra un NT.
Ese es el problema, que cualquiera administre.
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Martin Marques                  |        mmarques@unl.edu.ar
Programador, Administrador      |       Centro de Telematica                      Universidad Nacional                           del Litoral
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