The following paper can be cited when referring to Fityk:
Marcin Wojdyr, Fityk: a general-purpose peak fitting program, Journal of Applied Crystallography, 2010, Volume 43, pages 1126-1128. (reprint)
The list below is not maintained since 2010. You may use your favourite citation index instead, for example here is a link to fityk citations in Google scholar:
Publications which mention fityk. Although this list is not maintained since 2010, feel free to add your paper.