SQL & PL/SQL

I am trying to pull data out of Oracle Payables - invoices for which the invoice amount ,the vendor and distribution line count is same.
I could achieve pulling invoices with same Vendor having same amount.But finding hard to compare the counts.
Can anyone share ideas on how to achieve this ... Tried self join but did not work.
The query which I used is as follows :

select invoice_num,invoice_id,invoice_amount,vendor_id,
(select vendor_name from apps.po_vendors where vendor_id=aia.vendor_id) vendor_name,
(select count(*) from apps.ap_invoice_distributions_all aid where aid.invoice_id=aia.invoice_id) line_count
from apps.ap_invoices_all aia
where invoice_amount in (select aiab.invoice_amount
from apps.ap_invoices_all aiab
where aiab.creation_date >='01-AUG-2012'
and vendor_id=aia.vendor_id
group by aiab.invoice_amount
Having (count(aiab.invoice_amount) >1))
and aia.creation_date >='01-AUG-2012'

Thanks in Advance.