The expression for the probability that a given candidate is not the
true identification (equation 
) is not followed exactly be all
authors: de Ruiter et al. [2] replace it by
However, this approach is rejected by subsequent papers [5,6] because it relies on the assumption that the closest candidate is always the true identification, which is not the can when the background density is high.
The need to consider the magnitude of the candidate in estimating the
background density is widely recognised [5,6,9] and
in equation we will use 
, the density of
background objects with magnitude less than or equal to that of the
candidate.