Ratios of line fluxes in units of erg cm^-2 s^-1 as a function of logarithm of density of the pre-shock gas, n_H. Ratios of different transitions of the same molecules are shown at the top row and line ratios comparing different species are shown at the bottom. Filled symbols and full lines show models of C shocks (circles – from Kaufman & Neufeld, diamonds – from Flower & Pineau des Forêts), whereas the empty symbols and dash-dotted lines show models of J shocks (Flower & Pineau des Forêts 2010). Colors distinguish shock velocities: 20 km s^-1 shocks are shown in red, 30 km s^-1 in blue, and 40 km s^-1 in orange.