Fixes missing citation in dpf proceedings

dpf2019/proceedings.tex

@@ -138,6 +138,9 @@ CMS Collaboration. ``Search for production of four top quarks in final states wi
 \bibitem{tttt2016}
 V. Khachatryan et al. ``Search for standard model production of four top quarks with same-sign and multilepton final states in proton-proton collisions at $\sqrt{s} = 13 \mathrm{TeV}$''. In: \emph{Eur. Phys. J. C} 76 (2016), p. 439. DOI: 10.1140/epjc/s10052-016-4261-z. arXiv: 1605.03171 [hep-ex].
 
+\bibitem{SUS-15-008}
+V. Khachatryan et al. ``Search for new physics in same-sign dilepton events in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$''. In: \emph{Eur. Phys. J. C} 76 (2016, p. 439. arXiv: 1605.03171 [hep-ex].
+
 \bibitem{TopYukawaTTTT}
 Qing-Hong Cao, Shao-Long Chen, and Yandong Liu. ``Probing Higgs width and top quark Yukawa coupling from ${\rm t\bar{t}H}$ and ${\rm t\bar{t}t\bar{t}}$ productions''. In: \emph{Phys. Rev. D} 95 (2017), p. 053004. DOI:10.1103/PhysRevD.95.053005. arXiv: 1602.01934 [hep-ph].