Branch classification diagram plotted as the pEW of Si IIλ6355 against the pEW of Si IIλ5792 for the subtypes of our subluminous SNe Ia (91bg-like, 86G-like, 04gs-like, and 02es-like) with spectra between −5 and +5 days with respect to maximum light, showing the spectral classification into four subclasses on the diagram: core normal (CN), shallow silicon (SS), broad line (BL), and cool (CL). Additionally, the calculated spectral averages for the three subtypes (91bg-like, 86G-like, and 04gs-like) at the epoch of maximum light (−2 < d < +2) are plotted on the branch diagram and the distributions of the pEWs for all subtypes are as shown in the legend.