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.
Carl G. Jockusch Jr.. The Degrees of Hyperhyperimmune Sets. Journal of Symbolic Logic, 34(3):489-493, 1969.