In mid-June 2013, a new publication model, Electronic-eCollection, was introduced for PubMed citations from electronic-only journals. “Electronic-eCollection” means that an article is published electronically on a specific date and is also associated with an electronic collection date (similar to an issue; this date can be a year or a year and month, but never a year, month, and day). NLM determines the publication model based on the data submitted by the publishers.
“eCollection” will be displayed preceding the collection date information in a citation. The specific article date will display after the journal title abbreviation while the collection date will display near the end of the source information.
This particular article was published online on January 25, 2013, yet was included in the Volume 3, 2012 collection as deposited in PMC.