I know that the field of deep learning / machine learning generally moves too fast for researchers to target conferences or journals, but several of the citations in the PDF of this article are missing (LaTeX inserted [?]).

(GRU, in case anyone is wondering, stands for "gated recurrent unit" and is a building block of standard LSTMs)

EDIT: now that I've finished the paper, I've realized that the citations are straight-up missing. That's no good, but I'm sure the authors just messed up the arxiv upload. If OP knows them, they should let them know... failing to include any citations at all is a quick way to decrease the credibility of an article.