Of this group, 2 were published in 2008, 4 in 2009, 2 in 2011, and 1 in 2012, showing that there has been sustained research interest on the subject.
Entre ellos, 2 fueron publicados en 2008, 4 en 2009, 2 en 2011 y 1 en 2012, representando el sostenido interés de los investigadores por el tema.