Researchr is a web site for finding, collecting, sharing, and reviewing scientific publications, for researchers by researchers.
Sign up for an account to create a profile with publication list, tag and review your related work, and share bibliographies with your co-authors.
Nathan Goodman, Oded Shmueli. Tree Queries: A Simple Class of Relational Queries. ACM Trans. Database Syst., 7(4):653-677, 1982. [doi]