where dn1 and dn2 are the distances from each element to the corresponding source, sn1 and sn2 were used to reduce the penalty due to the distance between a source and a part of the solution near the other source. This means that a large dipole magnitude solution near to one source should not give rise to an improper error estimate due to the potentially large distance to the other source. sn1 can be chosen in the following way:
