A working paper is not examined by a publisher before publication, nor does the availability of a working paper online exclude an article from being considered for publication. However, papers which report new research or extend previous work are more likely to be accepted for publication. Working papers are usually prepared for conferences or special issues of journals, although some publishers will also consider them for other forms of publication such as books. The length of working papers varies but most are about 15 pages long including references. Authors typically have the opportunity to revise their work following peer review. Working papers are different from articles that appear in academic journals. An article is reviewed by peers and must meet certain criteria to be considered for publication. It can report new research or it can discuss existing studies or theories. Articles often include comments from authors regarding their main findings as well as discussions concerning other topics related to its subject matter. Working papers are usually produced by researchers while they are still studying or preparing material for conferences or books. They may report on their own work or others' research. As such, working papers can sometimes be seen as pre-prints of future articles or presentations. Authors should be aware that working papers which report new research cannot be used for applying for grants or hiring employees.