Zhang, B., G. M. Bisci, and M. Xiang. “Multiplicity Results for Nonlocal Fractional $p$-Kirchhoff Equations via Morse Theory”. Topological Methods in Nonlinear Analysis, vol. 49, no. 2, Nov. 2016, pp. 445-61, https://apcz.umk.pl/TMNA/article/view/TMNA.2016.081.