Thanks for correction. I didn't hear these names before and thought you just know them because you're classical music follower. Usually, I assumed that only Russians known worldwide get the English translit. Can you tell your favorite examples?
In Gubaidulina's case that would be the epic
Johannes Passion. You're welcome to just dip into it!
https://www.youtube.com/watch?v=akk7MuJWIegAs for Ustvolskaya, I remember being blown away when I first watched (and heard) this performance of her
Symphony No. 2:
https://www.youtube.com/watch?v=ynhdxHOrPm4