Carrying out the survey of the related researches is an essential part in research activities, the aim of which is to have an overall view of the target field. Generally, we take two approaches toward this aim. One approach is paying attention to selected articles and deeply investigate them. The selection is performed according to some indicators for measuring importance. The other approach is considering the citation relations between articles. One problem is that these approaches cannot be combined straightforwardly. Another problem in carrying out the survey is that there are a huge amount of articles exist already. The aim of this paper is to propose a framework of a visualization system that assists us in surveying related researches. The system displays the important articles together with their key citation relations by displaying not only direct citations between important articles but also the indirect, or weak-tie, citation relations that connect them.