 In their research on footnotes in scholarly journals in the field of communication, Michael Bugeja and Daniela V. Dimitrova have found that citations to online sources have a rate of decay (as cited pages are taken down), which they call a "half-life", that renders footnotes in those journals less useful for scholarship over time.Other experts have found that published replications do not have as many citations as original publications.Another important issue is citation errors, which often occur due to carelessness on either the researcher or journal editor's part in the publication procedure.