O. Baigenzhenov, S. Yulussov, Khabiyev А., Sydykanov М., and M. Akbarov, “Investigation of the leaching process of rare-earth metals from the black shale ores of greater Karatau”, Kompl. Ispolz. Min. Syra = Compl. Use of Min. Resour., vol. 310, no. 3, pp. 76–80, Sep. 2019.