This is the previous letter Abp. Vigano refers to:
https://archive.vn/NQyZe
https://www.lifesitenews.com/news/abp-vigano-raises-concerns-about-the-cardinal-put-in-charge-of-the-next-papal-election
In a statement released on January 31 and titled “The faithful have the right to know” (see official English text below), Archbishop Viganò asserts that Pope Francis’s confirmation of Cardinal Leonardo Sandri as Vice-Dean of the College of Cardinals is a “masterpiece of deception.”