In the early years American players would simply be recruited from the - then plentiful - American military installations in Germany which in part helps explain the early dominance of Frankfurt (near Rhein-Main Air Base) and Ansbach (site of several US armed forces facilities). However, with the drawdown of US forces in the mid 1980's and the increase in talent and professionalism throughout the league, a more formalized mechanism was put in place to recruit and fly in former college football players to play in Germany for pay as well as room and board. In 1982, the number of American "imports" was reduced to four, in 1983 to three and, by 1986, only two were allowed on the field for a team at any given time. In November 2010, a new Bundesspielordnung, the rule book of American football in Germany, was published. One major change was that the sport now placed citizens of European Union countries on equal footing with German nationals, meaning, restrictions on the number of these players per team on the field were now not in place anymore. However, the restrictions on non-EU nationals remained in place, unless those players could prove that they had spent at least three years playing for a youth team in the sport in Germany. This was an update in part mandated by the Bosman ruling (which established a precedent for association football but applies to all professional sports) and the rules on Freedom of movement for workers in the European Union. For the 2011 season, a club can sign up up to ten non-EU players, have six of those on the line-up for any given game but only two of those on the field at any given time. Players are marked with an "A" on their jersey and helmet to allow referees to determine at a glance whether the limit is obeyed on the field. These restrictions are specifically in place for US, Canadian, Mexican and Japanese citizens and, on request, exemptions can be made for players from countries without established structures in the sport. This rule is designed to prevent an advantage to the wealthier clubs, who could otherwise recruit a large number of players from the traditional American football countries. However, the aforementioned inevitable exception for EU citizens provides a strong incentive to sign players with dual nationality who have played college football but do not count as "Americans".