* here is the original paper : http://ai.unibo.it/sites/ai.unibo.it/files/u11/pso.pdf
* Then, a great paper by maurice clerc on Standard PSO : https://hal.archives-ouvertes.fr/hal-00764996/document
* Another one on particles confinment into the search space : http://hal.archives-ouvertes.fr/hal-00122799
* The contrition factor to control speed : https://www.semanticscholar.org/paper/The-particle-swarm-explosion%2C-stability%2C-and-in-a-Clerc-Kennedy/91e291f690b42120915abedda363210dc0aa2cbf
* A phd thesis, with info on exploration/exploitation dilemma https://repository.up.ac.za/bitstream/handle/2263/24297/00thesis.pdf?sequence=1
But there are many many more variants (FIPS, barebones PSO, ...), many studies on neighborhoods topology (ring, pyramids, von neumann, four clusters...)
So much great studies on this dense algorithm.
I let Pr Patriksson armada to discuss about how useless such methods are... ;) :D :D