Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:(51) is simplified into
Hðp; qÞ ¼ 1 N XN t¼1 0:5 lnjWðxtÞWTðxtÞj þ ln qðytÞ ; ð109Þ
which is exactly the cost function that leads to the nonlinear LPM-ICA algorithm (or particularly the LPM-ICA algorithm at the special case f ðrÞ ¼ r) (Xu, Yang, & Amari, 1996; Xu, 1998b; Xu et al., 1998).
Category: