The Law of Succession used is Agnatic Primogeniture. Chief forms are "agnatic seniority" and "agnatic primogeniture". In matters of inheritance, the Zhou dynasty recognized only patrilineal primogeniture as legal. The Netherlands established absolute cognatic primogeniture instead of male preference primogeniture by law in 1983. Luxembourg also used agnatic primogeniture until 20 June 2011, when absolute primogeniture was introduced. Spain uses the system of male-preference cognatic primogeniture. However, according to Tacitus the German tribe of the Tencteri employed patrilineal primogeniture. The heir is determined through two mechanisms&colon; absolute cognatic primogeniture and proximity of blood. Spain today continues this model of succession law, in the form of cognatic primogeniture. Oman is an absolute monarchy by male primogeniture. In a system of absolute primogeniture that disregards gender, female heirs apparent occur. The succession order is determined by primogeniture in most European monarchies. In 1506 Albert decreed that the duchy should pass according to the rules of primogeniture. The Egyptians also attached significance to primogeniture and birthright. Fraternal polyandry achieves a similar goal to that of primogeniture in 19th-century England.