The aim of this work is to assist in the determination of the (unbeknown) sources of the 1917 GRAE. We start from the base of 1911 GRAE and a little known document by monographer Julio Cejador y Frauca (1864-1927) that appeared in the Nuevo Mundo magazine on May 10th 1918. In said article, Cejador accuses the Academia of “plagiarizing” his work La Lengua de Cervantes (1905), especially, his syntactic ideas, both theoretical and descriptive. The research carried out in this work allows one to conclude that, despite the similarities and the specific coincidences between GRAE1917 and Cejador-1905, the academic syntax is not, strictly, the one in the 1905 work. Furthermore, common sources like Benot or Gisbert and Höel could be postulated.