  The cross section of the $t\bar{t}Z$ and $t\bar{t}W$ processes are measured
in a simultaneous fit using 36.1 $\text{fb}^{-1}$ of proton-proton collisions
at a centre of mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector
at the LHC. The result is found to be $\sigma_{t\bar{t}Z} = 0.95 \pm 0.08
\text{ (stat.)} \pm 0.10 \text{ (syst.)}\,\text{pb}$ and $\sigma_{t\bar{t}W} =
0.87 \pm 0.13 \text{ (stat.)} \pm 0.14 \text{ (syst.)}\,\text{pb}$ and
compatible with the Standard Model.
