The simplest cases are the closed-list systems where the voters cannot express preferences inside the lists. In this case, the political parties have a very substantial power, since they determine the order in which candidates are elected. In the case of open-list systems, the voters determine, at least up to a certain extent, the position of each candidate on the list which they compose. In addition, there are a few specific systems that can be classified among the open-list systems, which are the single transferable vote, cross-voting (panachage) and open or blank lists, which inherently incorporate a system for allocating seats within lists.