(<=> (Group ?Domain ?Op ?Id) (And (Binary-Operator-On ?Op ?Domain) (Associative ?Op ?Domain) (Identity-Element-For ?Id ?Op ?Domain) (Invertible ?Op ?Id ?Domain)))
(<=> (Group ?Domain ?Op ?Id) (And (Binary-Operator-On ?Op ?Domain) (Associative ?Op ?Domain) (Identity-Element-For ?Id ?Op ?Domain) (Invertible ?Op ?Id ?Domain))) (Subrelation-Of Abelian-Group Group) (<=> (Abelian-Group ?Domain ?Op ?Id) (And (Group ?Domain ?Op ?Id) (Commutative ?Op ?Domain))) (<=> (Division-Ring ?Domain ?Plus-Op ?Zero-Id ?Mult-Op ?One-Id) (And (Ring ?Domain ?Plus-Op ?Zero-Id ?Mult-Op ?One-Id) (Group (Kappa (?X) (And (Instance-Of ?X ?Domain) (/= ?X ?Zero-Id))) ?Mult-Op ?One-Id)))