rows duplicating in query reuslt

Hi,

If we create a query and the output of query show duplicate rows,so what does it mean?how can i find the problem.

Below is my created query but it shows 4 rows ,it should be show only 2 rows.mean 2 rows are duplicating

SELECT *

FROM gl_import_references gli 

, xla_ae_lines xll 

, xla_ae_headers xlh 

, xla_distribution_links xld 

, ap_invoices_all api 

, ap_invoice_lines_all apl 

, ap_invoice_distributions_all adp 

, gl_je_lines jel 

, gl_je_headers jeh 

WHERE 1 = 1 

AND api.invoice_id = apl.invoice_id 

AND apl.invoice_id = adp.invoice_id 

AND apl.line_number = adp.invoice_line_number