Q. CMOS 14.233 calls for URLs to be included in citations of online reference entries. But in the case of the OED (and probably other such premium sources), the URL will not work unless you have either a personal subscription or institutional access via a proxy server. So . . . what to do? Forgo the URL?
A. Include the URL, which will be helpful for some readers and may encourage others to find out if their library has a subscription to the resource that would give them access through their library membership. This isn’t much different from citing a printed book, which readers would usually be expected to find at a library or bookstore.