Vito, F., Gilli, R., Vignali, C., Comastri, A., Brusa, M., Cappelluti, N., & Iwasawa, K. (2014). The hard X-ray luminosity function of high-redshift (3 < z ≲ 5) active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 445(4), 3557-3574. doi:10.1093/mnras/stu2004.