Last name(s) in essays/criticism

[Queli]

I am hoping someone knows the definitive "answer" here (or if it is in flux or open to debate, could tell me about that). When writing about a Spanish or Latinamerican author who uses his/her name in a traditional form (first name, father's last name, mother's), how do you cite them when referring to them by last name (i.e. in a work of literary criticism)? I see it both ways and am confused as to which is correct. For example, most of the time I see "Vargas Llosa" when people are writing about for Mario Vargas Llosa but "Fuentes" only for Carlos Fuentes Macías. If anyone knows links that discuss this, that would be interesting too--my preliminary search only gave me how to put names in a bibliography.

[JPablo]

I don't know sources, or links, but I'd think it has to do with "how common" is the second name.

I.e.
Rafael Sánchez... (may be there are thousands of people with that name)
Rafael Sánchez Ferlosio (I only know one)

Federico García (Thousand of persons with this name)
Federico García Lorca (Only one...)

Arturo Pérez (a bunch of people with this name)
Arturo Pérez Reverte (I only know one with this one)

And so on and so forth.

Carlos Fuentes, Octavio Paz, Pablo Neruda (pen name, if I remember well), Julio Cortázar... are "unique enough" so as to not needing any additional name...

El Marqués de Santillana (even though there are many "Marqueses de Santillana") is only referred to the guy who wrote "Serranillas" and had one of the biggest libraries in what could be called "Spain" (or Castilla)...

Juan Goytisolo... (only one of those)

Julio Iglesias Snr. y Julio Iglesias Jnr. oops, sorry this one is not a writer...

[Queli]

This is great--makes a lot of sense! And as the Iglesias's show (who knew they'd appear in one of these threads?!) I would guess it also matters how the person refers to him/herself if it's a living person.

[JPablo]

Glad to be of help...

I was just kidding with J. Iglesias... (his full name being "Julio José Iglesias de la Cueva" per Wikipedia...) but it gives you even more of an idea on how names are used in Spanish...