The relationship between the [Oiii]λ4959/[Oiii]λ5007 flux line ratio and the equivalent width of [Oiii]λ5007 (left) and of the [Nii]λ6548/[Nii]λ6584 flux line ratio and the equivalent width of [Nii]λ6584 (right). The solid line gives the theoretical value (1/3). Empty triangles are for galaxies observed in this work, filled triangles for those presented in Gavazzi et al. (2004), red dots for objects in Jansen et al. (2000). Galaxies hosting an AGN are marked with a blue symbol. The vertical line indicates a 18% error in the flux line emission line.