I have at least some information for you.
You can read more here:
(1)
ewtn.com/library/PAPALDOC/P6601119.HTM
(2)
ewtn.com/library/PAPALDOC/P6691126.HTM
Also, if I can just give you my hearty encouragement to simply do your best to ignore the sedevacantists and those who are sympathetic to the SSPX.
Forgive me, but they present an “authentic” Catholicism that is like a mirage, and that does nothing other than cause a person to chase shadows, and that only drives a wedge between that person and the Magisterium.
The best apologetic against them is to trust the Church and those whom Christ has entrusted His Church to. Trust is the antithesis of these groups, who seek to cultivate doubt and to sow discord and confusion. If you find yourself struggling, you are experiencing the spiritual attack these groups are a channel for.