Today's post is interactive. Someone came in today with this very question, and it seemed to be one of wider interest.
When writing an essay you need to ensure your cited references are (a) recent and (b) from peer reviewed journals.
The up to date bit is easy enough. Any paper that you photocopy or print will have a date on it somewhere.
But what about the peer reviewed bit of it? How do you know if something is peer reviewed? Come to that - what IS peer review? It always makes me think of an elderly, dusty old party squinting myopically at a pile of papers...
Peer review, also known as refereeing, basically means asking people in the same field of expertise to have a look at any paper submitted for publication. These reviewers or referees check the paper for problems or weaknesses and may make suggestions for improvement.
The problem with this is that it's time consuming. If you've discovered something new and important it must be frustrating to have the paper announcing your findings held up for months while various people look at it. Some journals will actually show the data a paper was submitted, and the date it was accepted for publication (both dates can be some time before publication).
Sense About Science has a nice guide to peer review, written for the layperson in ordinary language. Peer review is supposed to improve the quality of articles, but doesn't guarantee that papers are free from errors. Not everyone thinks peer review is a good idea. And what about evidence that peer review works? Because asking if a paper is peer reviewed is just a part of the process of assessing the quality of evidence.
How do you know which journals are peer reviewed? When I was asked this today my first reaction was that you don't. Certainly an individual paper wont stat on it that it's peer reviewed. For that information you need the paper journals (remember those?) or the journal's website. Somewhere under information for authors, perhaps, or in a statement about the journal's purpose and readership) it will state that the journal is peer reviewed, that papers are refereed or give instructions for referees.
My second reaction was that surely there is a list somewhere. But there isn't. Now, wouldn't that be a nice project for someone...