Berkovits J, Leinfelder H, Mustonen V. Existence and multiplicity results for wave equations with time-independent nonlinearity. TMNA [Internet]. 1 grudzień 2003 [cytowane 22 lipiec 2024];22(2):273-95. Dostępne na: https://apcz.umk.pl/TMNA/article/view/TMNA.2003.040