Any information or document worth purchasing that will help you document your family name and past generations will come from the period BEFORE emigrating. Especially if you know the exact place of origin and have established contact with the descendants of the same family.
ERDELJ, ERDELJI, ERDELJAN, ERDELJAC, ERDELJAK and ERDELJANOVI? surnames are present among the Serbsthat originated from their settling in what is today Romania during XV and XVI century - one of its regions is in Hungarian language called *Erdely* . These families and the surnames spreadlater through further migrations in XVII, XVIII and XIX century all over former Yugoslavia .