Burke, J. D., Wittchen, H.-U., Regier, D. A., & Sartorius, N. (1990). Extracting information from diagnostic interviews on co-occurrence of symptoms of anxiety and depression. In J. D., Maser, & C. R., Cloninger (Eds.), Comorbidity of Mood and Anxiety Disorders (pp. 649-667). Washington, D.C.: American Psychiatric Press.