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———. 2014c. McGraw-Hill Education Intermediate Spanish Grammar. McGraw-Hill Education - Europe.
———. 2014d. McGraw-Hill Education Intermediate Spanish Grammar. McGraw-Hill Education - Europe.
Collins Spanish Dictionary & Grammar. 2018. 8th Edition. Glasgow: HarperCollins Publishers.
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Pinilla, Raquel, and Alicia San Mateo. 2016a. El Expres: Exercises Book Levels A1, A2, B1: Curso Intensivo de Espanol. Alcobendas (Madrid): SGEL.
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