The fixed point theory of complexity, Abstract of a contributed talk to the 12th Panhellenic Logic Symposium held in Anogeia, Crete, June 26 - 30, 2019, 6 pages.

Intuitionism and effective descriptive set theory, with Joan R. Moschovakis, Indagationes Mathematicae, vol. 29(2018), pp 396 - 426. Available online at www.sciencedirect.com.

Hyperarithmetical sets, in
*Martin Davis on computability, computational logic and
mathematical foundations*, edited by Eugenio G. Omodeo and Alberto
Policriti, Springer International Publishing, 2017, pp. 187 - 208.

On the Church-Turing Thesis and relative recursion, Proceedings of the 14th International Congress in Logic, Methodology and Philosophy of Science (Nancy 2011), published by College Publications in 2014, pp. 179 - 200.

Classical descriptive set theory as a refinement of effective descriptive set theory. Annals of Pure and Applied Logic, vol. 162 (2010), pp. 243 - 255.

Kleene's amazing second recursion theorem. The Bulletin of Symbolic Logic, vol. 16 (2010), pp. 189 - 239.

Kleene's amazing second recursion theorem (extended abstract), in Springer LNCS # 5771 (2009), ed. E, Grädel and R. Kahle, pp. 24-39.

Two aspects of situated meaning,
with Eleni Kalyvianaki, in *Logics for Linguistic Structures,*
edited by Fritz Hamm and Stephan Kepser, Mouton de Gruyter, Berlin, New York, 2008,
pp. 57 - 86.

Elementary
algorithms and their implementations ,
with Vasilis Paschalis, in *New
Computational Paradigms, *ed. S. B.
Cooper, Benedikt Lowe and Andrea Sorbi, Springer, 2008, pp. 81 -
118.

Lower bounds for coprimeness and other decision problems in arithmetic, Extended abstract of a 2005 lecture, published in the Proceedings of the Seminaire: de Structures Algebriques Ordonnees, No 79, (8 pages). [The published version has some unfortunate typos, especially in the references to the bibliography which systematically point to the wrong papers; this version is the correct one.]

Arithmetic complexity, with Lou van den Dries, ACM Transactions on Computational Logic, vol. 10 (2009), pp. 1—49.

Recursion and complexity, in New Computational Paradigms: First Conference on Computability in Europe, CiE 2005, Amsterdam, The Netherlands, June 8-12, 2005. Proceedings. Springer Lecture Notes in CS. vol. 3526/2005. Editors: S. Barry Cooper, Benedikt Lowe, Leen Torenvliet.

Αλγοριθμική σημασιολογία: το νόημα ως προσδιορισμός αναφοράς (Algorithmic semantics: meaning as referential intension), with Eleni Kalyvianaki. In Greek. To appear in a volume of articles which will be published by the Greek Mathematical Society. Posted on August 31, 2004.

Is the Euclidean algorithm optimal among its peers?,
with Lou van den Dries, *The
Bulletin of Symbolic Logic*, v. 10
(2004), pp. 390 -- 418.

A
logical calculus of meaning and synonymy ,
*Linguistics and Philosophy,*
v. 29 (2006), pp. 27 -- 89.

On primitive recursive algorithms and the greatest common divisor
function, *Theoretical
Computer Science, *v. 301 (2003), p. 1
-- 30.

What
is an algorithm? , *Mathematics unlimited -- 2001 and
beyond*, edited by B. Engquist and W.
Schmid, Springer, 2001, pages 919-936.

Mathematical logic,26 pages, Encyclopedia of Physical Science and Engineering.

The logic of recursive equations , with A. J. Hurkens, Monica McArthur, Lawrence Moss and Glen Whitney. The Journal of Symbolic Logic, vol. 63 (1998), pages 451 - 478.

A
game-theoretic, concurrent and fair model of the typed
lambda-calculus, with full recursion ,
Published in *Computer
Science Logic, 11th Interenational Workshop, CSL '97*,
edited by Mogens Nielsen and Wolfgang Thomas, Lecture Notes in
Computer Science #1414, Springer, 1998, pp. 341 - 359.

On
founding the theory of algorithms.
Published in *Truth
in mathematics*, edited by H. G. Dales
and G. Oliveri, Clarendon Press, Oxford 1998, pp. 71 -
104.

Συνέντευξη στο Quantum (Interview in the Greek edition of Quantum, published in the July-August issue of 1997). In Greek.

The
logic of functional recursion , PDF file, 29 pages. Published in *Logic
and scientific methods*, M. L. Dalla
Chiara et al, eds. Kluwer Academic Publishers, 1997, pages 179-207.

Computable
concurrent processes , PDF file, 31
pages. Published in *Theoretical Computer Science*, v. 139 (1995),
pages 243--273.

Powerdomains,
powerstructures and fairness , with
Glen T. Whitney, PDF file, 15 pages. Published in *Computer
Science Logic*, L. Pacholski and J.
Tiuryn, eds. Springer LNCS #933, 1995, pages 382-396.

Sense and denotation as algorithm and value , Postscript file, 39 pages. In PDF format. Published in Lecture Notes in Logic, #2 (1994), Springer J. Oikkonen and J. Vaananen, eds. pages 210-249. Posted on February 15, 2007: There is a gap in the proof of the main Theorem 4.1 of this paper. Here is a correct (and more detailed) version of this proof, in PDF form.

A model of concurrency with fair merge and full recursion,
PDF file, 57 pages. Published in *Information and Computation*, v. 93
(1991), pages 114--171.

A
mathematical modeling of pure, recursive algorithms ,
PDF file, 22 pages. Published in *Logic
at Botik '89*, A. R. Meyer and M. A.
Taitslin, eds. LNCS # 363 (1989).

The formal
language of recursion, PDF file, 37 pages. Published in the
*Journal of Symbolic Logic*, vol 54 (1989), pp. 1216 - 1252.