Dear Mr. Franciosi,
Thank you for posting your request on History Hub!
We suggest that you contact the Federal'naia arkhivnaia sluzhba Rossii (Rosarkhiv) [Federal Archival Service of Russia], ul. Il'inka 12, 103132 Moscow, Russia
Also, we searched online and located the following information on Operation Citadel.
We hope this is helpful. Best of luck with your research!