Voltas, N., C. Hernández-Martínez, V. Arija, and J. Canals. “The Three-Year Developmental Trajectory of Anxiety Symptoms in Non-Clinical Early Adolescents”. Psicothema, vol. 28, no. Número 3, Dec. 2016, pp. 284-90, http://156.35.33.188/index.php/PST/article/view/11292.