Integrated intensities of pairs of molecular transitions in binary post-AGB stars (black), as well in O- and C-rich stars (blue and red). Blue and red lines represent the averaged values for O- and C-rich AGB CSEs (only in the case of detections). The X and Y axes represent the integrated intensities of the observed transitions in logarithmic scale and units of Jy km s^-1. The upper limits are represented bv arrows.