Notebook[List[Cell[BoxData[FormBox[GridBox[List[List[RowBox[List[SubsuperscriptBox[StyleBox["D", Rule[FontSlant, "Plain"]], RowBox[List["f", ",", "k"]], "r"], "=", RowBox[List[RowBox[List[UnderscriptBox["\[Sum]", RowBox[List["1", "\[LessEqual]", "l", "\[LessEqual]", "n"]]], SubsuperscriptBox[StyleBox["D", Rule[FontSlant, "Plain"]], RowBox[List["f", ",", "k"]], RowBox[List["r", ",", "l"]]]]], "=", RowBox[List[UnderscriptBox["\[Sum]", RowBox[List["1", "\[LessEqual]", "l", "\[LessEqual]", "n"]]], RowBox[List["\[Mu]", "(", RowBox[List[SubscriptBox[OverscriptBox[StyleBox["f", Rule[FontSlant, "Plain"]], "_"], RowBox[List["N", ",", "k"]]], ";", SubscriptBox[OverscriptBox[StyleBox["r", Rule[FontSlant, "Plain"]], "_"], RowBox[List["N", ",", "l"]]]]], ")"]]]]]]]], TagBox[StyleBox[TagBox[RowBox[List["(", RowBox[List["Eq", ".", "   ", "2"]], ")"]], Null, Rule[Editable, True], Rule[Selectable, True]], "EquationLabel", Rule[Deletable, False], Rule[ZeroWidthTimes, True]], Null, Rule[Editable, False]]]], Rule[RowSpacings, 2.], Rule[ColumnWidths, List[Fit, Automatic]], Rule[RowAlignments, Top], Rule[ColumnAlignments, List[TextAlignment, Right]]], TraditionalForm]], "Input"]]]