Quasars at z~6 and above: prospects for wide-and-deep X-ray surveys and results from current exploratory programs.
Journal article published in 2012 by
Roberto Gilli 
,
M. Mignoli ,
G. Risaliti,
C. Vignali,
A. Comastri ,
K. Iwasawa,
M.-G. Zamorani,
M. Salvati,
F. Civano,
M. Brusa,
Team Wfxt
,
M. Mignoli ,
G. Risaliti,
C. Vignali,
A. Comastri ,
K. Iwasawa,
M.-G. Zamorani,
M. Salvati,
F. Civano,
M. Brusa,
Team Wfxt
