"For example, if the FFB is a very long, very narrow body oriented in the z direction, the matrix Bij takes the form [ B xx B xy B xz B yx B yy B yz B zx B zy B zz ] = CH 0 ??? [ 0 0 0 0 0 0 3 ??? xz / r 2 3 ??? yz / r 2 3 ??? z 2 / r 2 - 1 ] , ( 7 ) where x, y and z are the coordinates describing the location of the FFB, r=(x2+y2+z2)???, and C is a constant determined by the size and magnetic susc" . . . .