Leon,M.;Levcenko,S.;Serna,R.;Bodnar,I.V.;Nateprov,A.;Guc,M.;Gurieva,G.;Lopez,N.;Merino,J.M.;Caballero,R.;Schorr,S.;Perez-Rodriguez, A.;Arushanov,E. "Spectroscopic ellipsometry study of Cu2ZnSnSe4 bulk crystals" Applied Physics Letters 105, 6, pp. - 2014 DOI: 10.1063/1.4892548