Cycle unit reference. This problem occurs as follows:, for example, Unit A; InterfaceUses B; IMPLEMENTENTEND.Unit B; InterfaceUses A; ImplementAionend. This causes a loop unit reference, usually we try to avoid this, but sometimes it is unavoidable, use the following solution Measures: Unit a; interfaceImplementationUses B; End.Unit B; InterfaceUses A; ImplementAionend.