@article{COCV_2020__26_1_A21_0,
     author = {Borisov, Denis and Cardone, Giuseppe},
     title = {Spectra of operator pencils with small {\ensuremath{\mathscr{P}}\ensuremath{\mathscr{T}}-symmetric} periodic perturbation},
     journal = {ESAIM: Control, Optimisation and Calculus of Variations},
     publisher = {EDP-Sciences},
     volume = {26},
     year = {2020},
     doi = {10.1051/cocv/2019070},
     mrnumber = {4068302},
     zbl = {1444.47023},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1051/cocv/2019070/}
}