[O] org-ref: various directories

[Michael Giepen]

Hello,

I just cannot get org-ref to accept various directories:

I tried

(setq org-ref-pdf-directory (quote (
"/home/mcg/thesis/library/folder1/"
"/home/mcg/thesis/library/folder2/"
"/home/mcg/thesis/library/folder3/"
)))


It would also suffice if I could include subdirectories of 
.../thesis/library/