Try ZoteroBib for a quick retrieve of citation using ISBN, DOI, URL, etc. It is a free service that helps you build a bibliography instantly from any computer or device, without creating an account or installing any software.
Zotero is free software that allows you to collect, manage and cite your references. It stores your references in the cloud, so you can view them from any internet-connected computer. This guide lists some useful introductory resources for Zotero.
Zotero - click on the word Zotero below to get the software