The Pepperdine University Libraries have purchased the New Palgrave Dictionary of Economics Online. This is a great resource if you are looking for authoritative, in-depth definitions for concepts such as “sovereign debt” or “arbitrage pricing theory.”
The entries are detailed and written by experts in the field of economics. For example, the entry on “principal and agent” was written by Joseph E. Stiglitz, the 2001 winner of the Nobel prize for economics. It is 9 pages long and contains a lengthy bibliography.
The New Palgrave Dictionary of Economics Online borrows some classic articles from the 1987 and 2008 print editions, but it is much more dynamic and is updated 4 times a year.