The printed statute books of the several states and territories of the United States, purporting to be printed under the authority of those states and territories, and any copy of any statute, or any part thereof, contained therein, having attached thereto the certificate of the secretary of state, under seal of the state, certifying the copy to be complete and correct, that the statute book, from which the copy is taken, is deposited in the Office of the Secretary of State or in the state library and is, by him, believed to have been received under the authority of the state and territory purporting to have enacted the same shall be presumptive evidence in all courts of the legislative acts, public or private, of those states or territories, respectively. When the statute as written is only a part of the law of a state or territory and it is affected by other facts of a legal nature existing in that state or territory, if the courts of such state or territory have deduced from the written words of the statute upon a particular state of facts a well understood rule of law, then such rule of law may be proved by the testimony or opinions of competent witnesses instructed in the law of that state, or by the introduction into evidence of the books of reports of cases adjudged in that state purporting to be the official reports thereof, or to have been published under the authority of such state, or as a part of the national reporter system or of any universally accepted system of reports of decided cases or the works of commentators of recognized authority on the law of the particular state involved.