Systems and methods for determining an article association measure are described. In one described method, a computer program receives a first article identifier associated with a first attribute and a second article identifier associated with a second attribute and determines a similarity measure of the first article identifier to the second article identifier based at least in part on the first attribute and on the second attribute. The similarity measure may provide a means for associating various article identifiers so that they may be, for example, retrieved and/or ranked in subsequent search queries.