This Bogdanov paper looks very interesting, but unfortunately it’s behind a paywall. Anyone have access?
S. V. Bogdanov (Orenburg, Russian Federation) Systematics of the Ancient Yamnaya Culture’s Complexes of the Eastern Ponto–Caspian Steppes in the Frame of Transfer of Ore Mining and Metallurgy Traditions into Northern Eurasia Dozens of informative complexes of the ancient Yamnaya culture dated by the early Bronze Age (IV — first half of III millennia BC) were found in the Ponto-Caspian steppes in the course of field studies conducted within the Ural-Caspian steppe region in Western Kazakhstan and Orenburg Oblast (Russian Federation) during the last decades. The northern subgroup of sites within the system of the Volga-Ural variation of the early Yamnaya culture comes from the Urals. Another zone, preliminary called “the Aral-Caspian zone”, can be found further southward, in arid steppes and semi-deserts of the Northern Caspian region within valleys of Uil, Emba and Irgiz rivers. The paper discusses systematics of cultural-chronological complexes within the indicated zones of the Volga-Ural variation of the early Yamnaya culture and considered issues of their genesis, relation to archeological sites and cultures from the adjacent regions, and transfer of ore mining and metallurgy traditions into Northern Eurasia.