  A new way to define the notion of $\C$-orthocenter will be displayed by
studying some propierties of four points in the plane which allows to extend
the notion of Euler's line, the Six Point Circles and the three-circles
theorem, for normed planes. In the present paper (which can be regarded as
extention of \cite{M-WU} in Minkowski plane in general) we derive several
characterizations of the Euclidianity of the plane.
