Four theoretical approaches were used: fragmentation theory by solving a Schrödinger equation with mass asymmetry as a variable to obtain the mass distributions of fragments; penetrability calculations similar to those used in traditional theory of alpha decay, and superasymmetric fission models, numerical (NuSAF) and analytical (ASAF). Superasymmetric fission models are based on the macroscopic-microscopic approach using the asymmetrical two-center shell model level energies as input data for the shell and pairing corrections. Either the liquid drop model or the Yukawa-plus-exponential model extended to different charge-to-mass ratios have been used to calculate the macroscopic deformation energy.