Villani, R., R. Gargano, C. Rovai, P. Milillo, L. Macarini, and G. Serviddio. “To Be or Not to Be: A Two Years Surveillance for a CA 19-9 Persistent Elevation before Cancer Diagnosis and Bone Metastases”. JOURNAL OF GERONTOLOGY AND GERIATRICS, Vol. 64, no. 3, Sept. 2016, pp. 112-5, http://www.jgerontology-geriatrics.com/article/view/174.