  Here we chronologically summarize briefly the developments of the Levi
(Hartogs' Inverse) Problem together with the notion of coherence and its
solution, shedding light on some records which have not been discussed in the
past references. In particular, we will discuss K. Oka's unpublished papers
1943 which solved the Levi (Hartogs' Inverse) Problem for unramified Riemann
domains of arbitrary dimension $n \geq 2$, usually referred as it was solved by
Oka IX in 1953, H.J. Bremermann and F. Norguet in 1954 for univalent domains,
independently.
  At the end we emphasize an open problem in a ramified case.
