Studies of ${B} ^{*{s}2}(5840)^0 $ and ${B} _{{s}1}(5830)^0 $ mesons including the observation of the ${B} ^{*{s}2}(5840)^0 → B ^0 K ^0_{S} $ decay in proton-proton collisions at $\sqrt{s}=8\,\text {TeV} $ - CMS collaboration (2303 authors) (2018)