Another problem is how to account for Indo-Iranian isolates which have been borrowed into Uralic [...which form part of...] the new vocabulary, which most probably was acquired by the Indo-Iranians in Central Asia.

The Indo-Iranian Substratum. Lubotsky, Alexander, in ―Early Contacts between Uralic and Indo-European: Linguistic & Archaeological Considerations‖, Suomalais-Ugrilainen Seura, Univ. of Helsinki, Helsinki, 2001.Quoted in Talageri, S. G. (2010). The Rigveda and the Avesta. New Delhi: Aditya Prakashan.