“…The inverse source problem has been vigorously studied. Thus Wang et al [30] applied reproducing kernel space method to solve an inverse space-dependent source problem, Wei and Wang [31] used a modified quasi-boundary value method, Zhang and Xu [37] employed the Cauchy data at one end, Tatar et al [26,27] considered it for a spacetime fractional diffusion equation and investigated a nonlocal inverse source problem, Cheng et al [4] used a spectral method to determine an unknown heat source term from the final temperature history in the radial domain and provided logarithmic-type error estimates for regularised solutions, Xiong and Ma [33] discussed a backward ill-posed problem for an axis-symmetric fractional diffusion equation. For other relevant results, the reader is referred to [3,9,12,14,28,[34][35][36].…”