, we obtain thus altogether three equations, from which we obtain, on taking into account the symmetrical property of the
,
in which, following Christoffel, the abbreviation has been used,
If we multiply (68) by
and sum over the
, we obtain thus altogether three equations, from which we obtain, on taking into account the symmetrical property of the
,
in which, following Christoffel, the abbreviation has been used,
If we multiply (68) by
and sum over the