Current management of xerostomia in head and neck cancer patients by Nathan, C-AO, Asarkar, AA, Entezami, P, Corry, J, Strojan, P, Poorten, VV, Makitie, A, Eisbruch, A, Robbins, KT, Smee, R, St. John, M, Chiesa-Estomba, C, Winter, SC, Beitler, JJ, Ferlito, A