Finally, it is often convenient to write the first argument as a subscript, hence <math>\Upsilon_e \langle f \rangle = \Upsilon \langle e, f \rangle.</math> | Finally, it is often convenient to write the first argument as a subscript, hence <math>\Upsilon_e \langle f \rangle = \Upsilon \langle e, f \rangle.</math> |