What does [epub ahead of print] on a citation mean ?
These are citations which publishers submit to PubMed for articles that appear on the publisher’s web site in advance of the journal release. Citations listed in PubMed as [epub ahead of print] may not be available to us until the print version of the journal is published. Many publishers limit online access to ahead of print articles to individual subscribers; charging others for obtaining the ahead of print article. If a Free link to the full-text article is provided, you should follow the link to obtain the article.