Understanding Ovarian Hypo-Response to Exogenous Gonadotropin in Ovarian Stimulation and Its New Proposed Marker—The Follicle-To-Oocyte (FOI) Index oleh Carlo Alviggi, Carlo Alviggi, Alessandro Conforti, Sandro C. Esteves, Roberta Vallone, Roberta Venturella, Sonia Staiano, Emanuele Castaldo, Claus Yding Andersen, Giuseppe De Placido