* The first one is that the organizers invite themselves. They may publish information about the recruitment of referees through official website, social media and job advertisements to attract experienced referees to participate in the competition.
* The second is to select referees from local football associations or football referees' associations. These organizations will recommend experienced referees to participate in the competition to enhance the fairness and professionalism of the competition.
Please note that the sources of referees may be different for specific events or organizations, so it is best to consult the organizers of relevant events or official channels directly to obtain the most accurate information.