The two main systems are the adversarial system and the inquisitorial system: The adversarial system: The parties themselves determine what evidence is brought before the tribunal, and the tribunal is not permitted to actively seek out evidence beyond that presented by the parties. It is required, though, to give the parties extensive opportunities to put forward their case and to challenge the case put forward by others. The adversarial system is based on a number of assumptions: that the parties are in the best position to decide what evidence is useful; that both parties have adequate financial resources and access to information to participate effectively in the process; and that there is no substantial power imbalance between the parties. In an adversarial system, one of the parties usually has the burden of proof. The inquisitorial system: Often found in Europe, this system requires the tribunal to conduct the investigation and collect the evidence. Adjudicators may have greater latitude to examine and cross-examine the parties and witnesses, and may even call witnesses on their own initiative. An inquisitorial system can help re-establish the balance between "weak" citizens and "strong" government, particularly if the adjudicator's authority to obtain information does not prevent the parties from also playing a substantial role in bringing forward evidence and making representations. In the inquisitorial system, the tribunal itself may have the burden of finding enough evidence to determine whether a party is entitled to a remedy.