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.
Henryk Rybinski, Boleslaw K. Szymanski. Multilevel information system-- Towards more flexible information retrieval systems. Inf. Process. Manage., 17(5):277-290, 1981. [doi]