“…Following the early biomechanical models of avascular tumor growth proposed by Greenspan [14], the bifurcation analysis [15,16,17,18,19,20,21,22], numerical simulations, and computational modeling [23,24,25,26,27,28,29] have contributed significantly to the tumor modeling area. Recently, tumor growth models with a necrotic core have also been developed and analyzed via the bifurcation theory [30,31,32,33,34,35,36].…”