The cession may be verbal or implicit, or it may be inferred from the behavior of the parties. While the cession does not have to be in writing, the parties may agree that it should be, in which case it will only be legitimate if it is in writing. If there is no written document, then the cession never took place. In the absence of a written agreement, it can be difficult to determine whether an oral cession has taken place. However, there are some factors that may indicate that a cession has been made. For example: (1) the parties may have acted as if a cession had been made; (2) they may have changed their relationship with respect to certain issues arising after the cession was said to have taken place; and (3) if one party denies that a cession was made, then the burden is on that party to prove this fact. It is important to recognize that a cession does not require an explicit transfer of sovereignty. Rather, it involves a change in the nature of that relationship. Thus, even if one country's government remains unchanged, the other country may still feel that it has ceded control over an issue by agreeing not to protest against a particular action. For example, let's say that Canada and the United States agree that Canada will not object if American soldiers are sent to Iraq.