Mathematical Foundations of Computer Science, Volume 1: Sets, Relations, and Induction (with D. Simovici), Texts and Monographs in Computer Science, Springer-Verlag, New York, 1991.

- The plus-cupping theorem for the recursively enumerable degrees (with R.I. Soare), in M. Lerman, J.H. Schmerl and R.I. Soare, eds., Proceedings of the Logic Year 1979-1980, Lecture Notes in Mathematics, Vol 859, Springer-Verlag, Berlin, 1981, 49-62.
- Branching degrees above low degrees, Transactions of the American Mathematical Society, 273, 1(1982), 157-180.
- The density of the nonbranching degrees, Annals of Pure and Applied Logic, 24, 2(1983), 113-130.
- Embeddings and extensions of embeddings in the r.e. tt- and wtt- degrees (with R.A. Shore), in H.D. Ebbinghaus, G.H. Muller and G.E. Sacks, eds., Recursion Theory Week (Proceedings of a Conference held in Oberwolfach, West Germany, April 15-21, 1984), Lecture Notes in Mathematics, Vol. 1141, Springer-Verlag, Berlin, 1985, 121-140.
- Infima of recursively enumerable tt-degrees (with R.A. Shore), Notre Dame Journal of Formal Logic, 29, 3(1988), 420-437.
- Degree theoretical splitting properties of recursively enumerable sets (with K. Ambos-Spies), Journal of Symbolic Logic, 53, 4(1988), 1110-1137.
- Embedding lattices with top preserved below non-GL2 degrees, Zeitschrift fuer Mathematische Logik und Grundlagen der Mathematik, 35, 1(1989), 3-14. dvi file ps file
- A direct construction of a minimal recursively enumerable truth-table degree (with R. Shore), in K. Ambos-Spies, G. Mueller and G. E. Sacks, eds., Recursion Theory Week (Proceedings of a Conference held in Oberwolfach, FRG, March 19-25, 1989), Lecture Notes in Mathematics, Vol. 1432, Springer-Verlag, Berlin, 1990, 187-204. dvi file ps file
- Embedding distributive lattices preserving 1 below a nonzero recursively enumerable Turing degree (with K. Ambos-Spies and D. Decheng), in J. Crossley et al., eds., Logical Methods: In Honor of Anil Nerode's Sixtieth Birthday, Progress in Computer Science and Applied Logic, Volume 12, Birkhauser, Boston, 1993, 92-129. dvi file ps file
- Decidability of the two-quantifier theory of the recursively enumerable weak truth-table degrees and other distributive upper semi-lattices (with K. Ambos-Spies, S. Lempp and M. Lerman), Journal of Symbolic Logic, 61, 3(1996), 880-905. dvi file ps file
- Lattice representations for computability theory, Annals of Pure and Applied Logic, 94 , 1-3(1998), 53-74. dvi file ps file
- Collapsing polynomial-time degrees (with K. Ambos-Spies, L. Bentzien, W. Merkle, F. Stephan), in S. Buss et al., eds., Logic Colloquium '98, Lecture Notes in Logic, Volume 13, Association for Symbolic Logic, Natick, MA, 2000, 1-24. dvi file ps file
- Every incomplete computably enumerable truth-table degree is branching (with R. Shore), Archive for Mathematical Logic , 40 , 2(2001), 113-123. dvi file ps file
- Embeddings of N5 and the contiguous degrees (with K. Ambos-Spies), Annals of Pure and Applied Logic , 112 , (2001), 151-188. dvi file ps file
- Enumerations of the Kolmogorov function (with R. Beigel, H. Buhrman, L. Fortnow, P. Grabowski, L. Longpre, A. Muchnik, F. Stephan, L. Torenvliet), Journal of Symbolic Logic , 71 , 2(2006), 501-528. ps file
- Degrees of unsolvability (with K. Ambos-Spies), to appear. pdf file

The 1991 Loebner Prize Competition (Dateline: Boston, November 8) (with W. Campbell), IEEE Expert, 6, 6(Dec. 1991), 47-48.