It maybe the all basis of the research – when there is no intention of collecting new data in the current project and it will be based entirely on the literature. It can be the source of ideas on what topics need researching. It may be an exercise to ensure that someone else has not already done the proposed research. It may be a source of ideas about the proposed of topic research, whether in terms of theories or methodology. It may be a source of comparison, where findings from previous related studies are compared with those of the proposed project. The information may be an integral or supportive part of the research, complementing the newly collected data – for example, the use of population census data or business customer records in conjunction with survey data