The historical development of the famous Einstein formula \ is briefly discussed. In this paper, on the basis of the Einstein viewpoint a new general approach is proposed for demonstrating the correctness of the formula \ . It is can be seen that the generalized approach leads to Einstein’s famous formula, too. During recent years, various papers have been published concerning the incompleteness of this famous formula. It is demonstrated that the presented claims in these articles are not mathematically legitimate. (...) It is clear that there are still some important misunderstandings concerning the interpretation of Einstein’s mass-energy equivalence formula. (shrink)