fact: Definition exercise6_11b_assumption X E:= [/\ union X = E, (forall A, inc A X -> nonempty A), (forall A B, inc A X -> inc B X -> A = B \/ small_set (A \cap B)) & (forall A B C, inc A X -> inc B X -> inc C X -> ( A=B \/ A = C \/ B = C \/ A \cap B = emptyset \/ A \cap C = emptyset \/ B \cap C = emptyset \/ (A \cap B = A \cap C /\ A \cap B = B \cap C)))].
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)