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:…as:
P xið Þ ¼ e aþ Pn j¼1 bjxij
1þ e aþ Pn j¼1 bjxij
: ð1Þ
Here P(xi) is the probability of detection (0–1) of MODIS pixel i based on the linear combination of ASTER fire pixel summary statistics ( j=1,n), and α and βj are parameters derived from the data (Agresti, 1990; Morisette et al., 2005b).
Category: