Lorca studies are curiously fragmented. Because of the vast amount of material, most articles, books, etc... won't be cited in most other articles, books. There is no way the average article could have a bibliography of 20 pages to even cover the minimum necessary. So people are free to cite quite selectively or sometimes hardly at all. Take Cifuentes '86 book La norma y la diferencia. It isn't cited much in Soufas's 96 book Audience and Authority, or in Paul Julian's Smith '98 book The Theatre of García Lorca. There are a few citations among these three books, if memory serves me, but there is no real dialogue or exchange of ideas in three excellent books on a similar topic. If a Lorca book is really bad, and I am not kicking its ass just to prove a point, then I won't cite it at all.
But I do think excellent scholars should cite one another.