But in the period 3100-2900 BC came a clear and dramatic infusion of Yamna [= Pontic] cultural practice, including burials, into Eastern Hungary and along the lower Danube. With this we are able to witness the beginnings of the Indo-Europeanization of Europe.
Source, in full
Fortson (2004:42-43) quoted in Elst, Koenraad (2018). Still no trace of an Aryan invasion: A collection on Indo-European origins. quoting Fortson, Benjamin, 2004: Indo-European Language and Culture. An Introduction, Blackwell, Oxford.