In a previous post fedorqui posed the question ¿Se debe escribir artículo delante de una palabra extranjera que ya lo contiene en su lengua? which referred to (mostly) newspaper titles from other languages which already contain the definite article. This raised in my mind the question of how we talk about Spanish language (SL) newspapers and magazines.
In some cases the name already contains the definite article so we say
Leo un artículo en El País
Leo un artículo en La Tercera
But it seems that if there is no article in the title we do not add it. For instance the SL Wikipedia refers to the paper simply as Clarín without adding "el" before it. So I assume I would say:
No he leído nunca un artículo en Clarín
I also notice that the sports paper As has a feature which it calls La chica de As and not del As.