Scaled Scrum - trusted source of information for PSM I exam

Hello Everybody,

I am currently studying to take the PSM I exam.

I am struggling a bit on the "scaled Scrum" part. It seems different authors have different approaches to Scaled Scrum.

I read a couple articles and books about this topic but I would like to know if you could give me recommendations of what to read that is aligned with the Scrum.org vision (on the scaled scrum topic).

Is the Nexus Guide enough?

I am asking this because I did, several times, the scaled scrum open exam and I feel that I still don't "master" this topic.

Thank you.