 the orthogonal projections) such that

(where formula_8 is the identity operator of formula_6) and for every formula_10, the following function formula_11

is a complex measure on "formula_2" (that is, a complex-valued countably additive function).We denote this measure by 
formula_14.Note that formula_15 is a real-valued measure, and a probability measure when formula_16 has length one.