It can also be written as a power series:formula_10or as:formula_11where sinc is the unnormalized sinc function and formula_12 is one of the imaginary, zero or real square roots of "k".
Splošna metrika, za katero ti pogoji veljajo, je:: formula_1kjer formula_2 zajema trirazsežni prostor s konstantno ukrivljenostjo: eliptični prostor, evklidski prostor ali hiperbolični prostor.