“…Asymptotic solutions to initial and boundary value problems based on the DO time-fractional diffusion equations can be found in [ 293 , 294 ]. Some additional and important mathematical aspects, such as the existence of the solution to different types of DO diffusion equations, the solvability of DO diffusion equations, subordination properties, and positivity of the solution were addressed in [ 59 , 63 , 263 , 287 , 295 , 296 , 297 , 298 , 299 , 300 ]. In a series of papers [ 71 , 72 , 301 ], Luchko analyzed the well-posedness of the DO formulation via maximal principles, and obtained a priori norm estimates for solutions to both linear and nonlinear DO diffusion equations.…”