Shwaysh Ahmed, M., I. Hayif Sameer, y M. T. Yassein Al-Heeti. «The Semantic Roles Which Cause Difficulty To The Fourth Year Students Of English At The University Of Anbar». Opción, Vol. 35, n.º 89, julio de 2019, pp. 343-68, https://www.produccioncientificaluz.org/index.php/opcion/article/view/31099.