Set Theory
Sets, Relations and Logic
Yet a bit more Introduction to Foundational Mathematics
Michael Prantl
Logic
Hard Proofs and Logic
Introduction to Mathematics for non-Mathematicians
Physics
A Finite Solution to Lorentz Factor at the Speed of Light
In theoretical physics, the Lorentz factor is a term by which relativistic mass, time, and length changes for an object in motion.
Logic
Formal Truth and Logic
Introduction to Logic for non-Mathematicians