GTC spectra of z ≈ 2.3 quasars: comparison with local luminosity analogs Jack W. Sulentic, Paola Marziani, Ascensión del Olmo, Deborah Dultzin, Jaime Perea and C. Alenka Negrete A&A, 570 (2014) A96 Published online: 29 October 2014 DOI: 10.1051/0004-6361/201423975