“…To the best of our knowledge, Tingley's problem remains open even for two dimensional spaces (see [5] where it is solved for non-strictly convex two dimensional spaces). A full machinery has been developed in the different partial positive solutions to Tingley's problem in the case of classical Banach spaces, C * -and operator algebras and JB * -triples (see, for example the references [2,5,8,10,11,15,16,18,19,20,30,32,35,36,38,39,43] and the surveys [47,37]).…”