Measurement of the $${\varvec{t\bar{t}Z}}$$ t t ¯ Z and $${\varvec{t\bar{t}W}}$$ t t ¯ W production cross sections in multilepton final states using 3.2 fb $$^{-1}$$ - 1 of $$\varvec{pp}$$ p p collisions at $$\sqrt{s}$$ s = 13 TeV with the ATLAS detector
European physical journal. C, Particles and fields