FADO spectral fit example, from Gomes & Papaderos (2017), for the metal-poor blue compact galaxies (BCD CGCG 007-025, yellow line) observed in the SDSS (see also Guseva et al. 2007). Panel a: best-fitting synthetic SED with stellar and nebular continuum emission, shown in blue, grey and red, respectively. Panel b: residuals between fit and observed spectrum; the shaded area and the dashed curve delineate the ±1σ and ±3σ error spectrum, respectively.