Prevalence of amyloid-β pathology in distinct variants of primary progressive aphasia. - Bergeron D; Gorno-Tempini ML; Rabinovici GD; Santos-Santos MA; Seeley W; Miller BL; Pijnenburg Y; Keulen MA; Groot C; van Berckel BNM; van der Flier WM; Scheltens P; et al. (Annals of neurology, 2018)