PerioLibros was a project for cultural dissemination by Fondo de Cultura Económica and UNESCO; works of literature were printed monthly as supplements to newspapers in 25 Spanish- or Portugese-speaking countries. See here for an image of no. 24 ("Aura") as a supplement to the broadsheet newspaper La República (Lima, Peru). Information from Worldcat and an article in the Enciclopedia de literatura en México. The binding size is likely "broadsheet" but that is not certain.