Solís, Abdel A., José A. Bethancourt, y Gabrielle B. Britton. 2008. «Chronic Sildenafil (Viagra) Administration Reduces Anxiety in Intact and Castrated Male Rats». Psicothema 20 (Número 4):812-17. https://reunido.uniovi.es/index.php/PST/article/view/8735.