2003A&A...412..651C

We are carrying out a multi-purpose program of high signal to noise optical spectroscopy at medium resolution of 30 BL Lac objects. Here we report the detection of three new redshifts, and the discovery of three misclassified sources. The new redshifts refer to PKS 0754+100 (z=0.266), H-1914-194 (z=0.137) and 1E S0715-259, for which we derive a redshift of z=0.465 and also a ``new'' classification a Steep Spectrum Radio Quasar. In two cases (UM 493 and 1620+103) stellar spectra indicate a wrong classification. The three sources with new redshift measurement show strong [OIII] emission in their spectra and their host galaxy properties are known. The central black hole masses derived using the M_BH-L_bulge and the M_BH-σ([OIII]) relations are compared.