Gorlero F, Nicoletti L, Lijoi D, Ferrero S, Pullè A, Ragni N. Endometrial directed biopsy during sonohysterography using the NiGo device: prospective study in women with abnormal uterine bleeding. Fertil Steril 2008;89:984-990. https://www.fertstert.org/article/S0015-0282(07)00970-3/fulltext