(1) If referral is made to the law of another State, the private international law of that State shall also be applied, insofar as this is not incompatible with the meaning of the referral. If the law of another State refers back to German law, the German substantive provisions shall apply.
(2) Referrals to substantive provisions relate to legal rules of the applicable legal system by the exclusion of its private international law. Where the parties can choose the law of a certain State, that choice may only relate to the substantive provisions.
(3) If referral is made to the law of a State having several partial legal systems, without indicating the applicable one, then the law of that State will determine which partial legal system shall be applicable. Failing any such rules, the partial legal system to which the connection of the subject matter is closest shall be applied.