API to read an allocation posting or the related CO journal entry

Dear Experts,

I am looking for a solution to read Allocation Postings via API.

The only released API related to allocation postings I can find is "Allocation Posting – Create (Synchronous)", no API in read mode.

As an alternative I am trying to read the corresponding CO journal entry via API_JOURNALENTRYITEMBASIC_SRV/A_JournalEntryItemBasic, unfortunately with no success (I cannot identify the relationship between the CO JE and the allocation posting document number).

Do you have any hints?

Thank you,

-Luca-