fact: Definition K4 := Conc (Star (Plus a (Conc b (Conc (Star c) d)))) (Conc b (Star c)).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegexpBrzozowski(glue gfinset regexp finite_der equiv) RegexpBrzozowski(sim1 sim2)