Need to Link pay_element_entry_values_f and fnd_attached_documents to get the right attachment raise

An entry of  club Benefits information is getting stored in pay_element_entry_values_f  and we are uplaoding the attachment and those are also shown in  fnd_attached_documents table . Now we wanted to find the link between these two tables to understand and link which document is raised against which club benefit . When we looked at both the tables we are not able to find a link . Please help us which tables to be considered to get the PK1_VALUE in fnd_attached_documents