Stellar mass-size relation for our basic sample and several other samples of compact massive early-type galaxies from the literature in comparison to our own data. The blueish cloud indicates the early-type galaxies of our basic sample. The black stars represent the candidates of our sample. The galaxies of the Ta10 sample are shown using filled green triangles and the galaxies of the Tr09 sample are denoted by filled cyan diamonds. The galaxies from Taylor et al. (2010), using the values of their paper, are indicated by open dark green triangles. The open blue diamonds represent the galaxies of Trujillo et al. (2009). Orange crosses mark the catalogue of various high redshift samples by van de Sande et al. (2013). The high redshift sample of Belli et al. (2014) is indicated by red Xs. Open brown nabla symbols mark the high redshift galaxies of Damjanov et al. (2009). Open magenta circles indicate the intermediate redshift sample of Zahid et al. (2015). NGC 1277 of van den Bosch et al. (2012), which is the only galaxy of their sample for which we have a stellar mass is represented by an filled violet circle. b19 using our calibration of SDSS data is shown by a filled grey square and b19 using the calibration of Läsker et al. (2013) is indicated by an open grey square. Because we use the values available in the literature to mark the positions of the galaxies in this plot, one has to consider potential systematics, especially in the effective radius R₀, which was measured in different filters by different authors. The dashed magenta line marks the limiting scaling radius for our sample selection.