The much lower entry cost of on-line publishing has also raised concerns of an increase in publication of "junk" journals with lower publishing standards. These journals, often with names chosen as similar to well-established publications, solicit articles via e-mail and then charge the author to publish an article, often with no sign of actual review. Jeffrey Beall, a research librarian at the University of Colorado, has compiled a list of what he considers to be "potential, possible, or probable predatory scholarly open-access publishers"; the list numbered over 300 journals as of April 2013, but he estimates that there may be thousands. The OMICS Publishing Group, which publishes a number of the journals on this list, has threatened to sue Beall.