Resources

History of Unified Field Theories p-II aka https://link.springer.com/article/10.12942/lrr-2014-5

http://relativity.livingreviews.org/ aka Springer journal 4114

2017/08/03 – The Atomic Nucleus as a Relativistic System  *sigh*  Just because you never heard the news, doesn’t mean it didn’t happen.  A Relativistic Gravitational Model Based on an Atom’s Behavior in a Gravitational Field

A good source for basic equations and brief descriptions:  hyperphysics.phy-astr.gsu.edu