• Lambert et al 2013

Bell's inequality experiment is important in understanding particle entanglement and the absence of unentangled “hidden states”. https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell_test_experiments

A YouTube video that does an excellent job of explaining Bell's inequality.

https://blogs.scientificamerican.com/critical-opalescence/how-to-build-your-own-quantum-entanglement-experiment-part-1-of-2/

https://blogs.scientificamerican.com/critical-opalescence/how-to-build-your-own-quantum-entanglement-experiment-part-2-of-2/

http://physicsopenlab.org/2016/02/20/entangled-gamma-photons/

https://spookyactionbook.com/2013/02/14/how-to-build-your-own-quantum-entanglement-experiment-part-2-of-2/

https://phys.org/news/2019-11-quantum-physics-reality-doesnt.html

https://phys.org/news/2019-10-peek-schrodinger-cat-disturbing.html