the operator of type $(V-A)\times (V-A)$ and the tensor one can accommodate current discrepancies, while the purely scalar ones cannot. These scenarios can be experimentally tested (i) by measuring similar LFU ratios based on the same quark transition, (ii) by studying the angular asymmetries of $B\to D^{(\ast)} \tau \bar{\nu}$ decays, and (iii) by studying purely leptonic observables, which are related to the LFU breaking effects via RGE effects. We have also argued that LQ bosons are the best candidates to explain these anomalies and we summarized the viable proposals made in the literature.

Acknowledgments {#acknowledgments .unnumbered}
===============

I would like to thank the organizers for the invitation and especially to Damir Bečirevi' c, Svjetlana Fajfer, Ferruccio Feruglio, Nejc Košnik and Paride Paradisi from whom I learned so much about the subject of this talk. This project has received support by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement N$^\circ$ 674896.

[99]{}

J. P. Lees [*et al.*]{} \[BaBar Collaboration\], Phys. Rev. Lett.  [**109**]{}, 101802 (2012) \[arXiv:1205.5442 \[hep-ex\]\].

J. P. Lees [*et al.*]{} \[BaBar Collaboration\], Phys. Rev. D [**88**]{}, no. 7, 072012 (2013) \[arXiv:1303.0571 \[hep-ex\]\].

M. Huschle [*et al.*]{} \[Belle Collaboration\], Phys. Rev. D [**92**]{}, 