Introduction to composite models - Theoretical models and experimental ramifications Giacomo Cacciapaglia, Aldo Deandrea and K. Sridhar Eur. Phys. J. Spec. Top., 231 7 (2022) 1223-1228 Published online: 07 March 2022 DOI: 10.1140/epjs/s11734-022-00445-5