This add-on is a plugin for Zotero, a research source management tool, which is a Firefox extension. The add-on automatically fetches numbers of citations of your Zotero items from Google Scholar and makes it possible to sort your items by the citations. Moreover, it allows batch updating the citations, as they may change over time.
When updating multiple citations in a batch, the plugins makes a 1 minute delay after every 50 items to try to avoid being blocked by Google Scholar for multiple automated requests. If a blockage happens, the add-on opens a browser window and directs it to http://scholar.google.com/, which may result in two distinct cases. In one case, Google Scholar displays a Captcha, which you need to enter to get unblocked and then re-try updating the citations. In the other case, Google Scholar displays a message like the following "We're sorry... but your computer or network may be sending automated queries. To protect our users, we can't process your request right now." In that case, the only solution is to wait for a while until Google unblocks you.
Currently, Zotero doesn't have any special field for the number of citations, that's why it is stored in the "Extra" field. To sort by this field you have to add it in the source listing table.
IMPORTANT: in version 1.8 the field for storing the number of citations has been changed from "Call Number" to "Extra" – please update your column configuration accordingly.
Version 1.9.3 supports Zotero 5!
The add-on also supports Zotero Standalone: