Abstract: A computer-implemented method for identifying a product citation in a document, the method comprising searching, in the document, for an entity identifier corresponding to an entity and, if an instance of the entity identifier is detected in the document, determining a portion of the document around the instance of the entity identifier as a target text, wherein the entity is associated with a product catalogue, the product catalogue comprising a plurality of product identifiers; applying a first regular expression to the target text, wherein the first regular expression is configured to match one or more of the plurality of product identifiers; and if a product identifier from the plurality of product identifiers is determined to be cited in the target text, adding an entry to a citation database linking the document and the product identifier.