Object Databases: The Essentials by Roberto Zicari · Published November 3, 2013 · Updated February 24, 2014 M. Loomis, Object Databases: The Essentials, Addison-Wesley, 1994, ISBN 0-201-56341-2
Seven Databases in Seven Weeks: A Guide to Modern Databases and the NoSQL Movement April 28, 2014 by Roberto Zicari · Published April 28, 2014