Thank you ~
Actually, I’ve tried the WP-admin setting of WP-Mendeley.
In the API keys section, I use the client_id (2-char) and the client_secret (16-char) to get authorize tokens, but get the {“error”:”Missing request oauth token.”}
I’m not sure whether it is because Mendeley will discontinue (April 14, 2014) the support of OAuth1. This page https://sites.google.com/site/mendeleyapi/home/authentication shows the details.