Distribution of psychogenic and vascular impotence in a tertiary health-care center's cohort: A retrospective study using penile Doppler imaging Bahri Gok; Nurullah Hamidi; Ozer Ural Cakici; Erdem Koc; Davut Kamaci; Erem Asil; Murat Keske; Ayse Nur Ozcan; Ali Fuat Atmaca;