The oral testimony of witnesses skilled therein is admissible as evidence of the unwritten law of any state or foreign country, as are also printed and published books of reports of decisions of the courts of such state or foreign country, as proved to be commonly admitted in such courts. SOURCE: CCP § 1902. CROSS-REFERENCES: § 201 of this Title; Rule 44.1 FRCP; Rule 26.1 FRCrP; 8 GCA § 95.80 [Criminal Procedure].