Understanding the Slate UI Architecture in Unreal Engine | Unreal Engine 5.1 Documentation
Gameplay Framework + Network | An Unreal Engine Blog by Cedric Neukirchen
Garbage Collection & Dynamic Memory Allocation - Old UE4 Wiki
Memory Management & Garbage Collection in Unreal Engine 5 | Mikelis' Game Blog
And math references:
Following this topic, finding more sources can’t hurt. Official documentation is not very in depth for programmers.