Example of the results of the Monte Carlo simulations for the number of double-lined PN occurring in the sample of 1135 observed with FLAMES. The spatial distribution of PNe is shown with the galaxy rotated (by 35°) with the major axis along the y-axis. The black crosses show the observed single-lined PN and the blue crosses all the double-lined PN (see Fig. 8); the red crosses show the simulated single-lined PN. The four double PN resulting from this particular Monte Carlo simulation are shown by the green pluses. No triple-lined PN were detected in this simulation. The central region masked out of the simulation corresponds to the extent of the dust lane (although a few PNe were detected in this area, including the triple lined PN EMMI_1098 and the double lined PN in the globular cluster H6).