Connecting MSEG to VBAP

Hi All,

I am trying to get a trace of the material documents found in MSEG back to VBAP-VBELN. The usually columns KDUAF, EBELN, EBELP and VBELN are empty. The only columns I have that are not null and look like a unique identifer are MBLNR, AUFNR, RSNUM, LGPLA, and AUFPL. Do any of these columns trace back to a sales order number (VBELN in VBAP)?

Thank you,

Gerardo