Ashcroft, R. J., R. Cvitkovic, and M. Praver. “Digital Flashcard L2 Vocabulary Learning Out-Performs Traditional Flashcards at Lower Proficiency Levels: A Mixed-Methods Study of 139 Japanese University Students”. The EuroCALL Review, vol. 26, no. 1, July 2018, pp. 14-28, doi:10.4995/eurocall.2018.7881.