Matt, Georg E., and Carmelo Vázquez. 2008. “Anxiety, depressed mood, self-esteem, and traumatic stress symptoms among distant witnesses of the 9/11 terrorist attacks: transitory responses and psychological resilience”. The Spanish Journal of Psychology 11, nº 2:: 503-15. https://revistas.ucm.es/index.php/SJOP/article/view/SJOP0808220503A