Mena Muñoz, S. and Martínez Fernández, J.L. 2012. Information and Entertainment Channels at Underground and Buses Systems in Spain. Estudios sobre el Mensaje Periodístico. 17, 2 (Jan. 2012), 531–548. DOI:https://doi.org/10.5209/rev_ESMP.2011.v17.n2.38129.