Printed books purporting to contain statutes, ordinances or other written laws
in force in any country, although not purporting to have been printed or
published by authority, and books purporting to contain reports of decisions
of courts or judges in such country, and text books treating of the laws of
such country, may be referred to by all courts for the purpose of ascertaining
the laws in force in such country; but such courts shall not be bound to
accept or act on the statements in any such books as evidence of such laws.