On the Complexity of Analytic Sets. - Karel Hrbacek (Math. Log. Q., 1978)

A New Proof that π. - Richard Gostanian; Karel Hrbacek (Math. Log. Q., 1979)

Degrees of analytic Sets. - Karel Hrbacek (Math. Log. Q., 1983)

Powerdomains as Algebraic Lattices (Preliminary Report). - Karel Hrbacek (ICALP, 1985)

A Powerdomain Construction. - Karel Hrbacek (MFPS, 1987)

Convex Powerdomains I - Karel Hrbacek (Inf. Comput., 1987)

Convex Powerdomains II - Karel Hrbacek (Inf. Comput., 1989)

Standard Foundations for Nonstandard Analysis. - David Ballard; Karel Hrbacek (J. Symb. Log., 1992)

Realism, nonstandard set theory, and large cardinals. - Karel Hrbacek (Ann. Pure Appl. Log., 2001)

Combinatorial principle in nonstandard analysis. - Mauro Di Nasso; Karel Hrbacek (Ann. Pure Appl. Log., 2003)

Standard sets in nonstandard set theory. - Petr Andreev; Karel Hrbacek (J. Symb. Log., 2004)

Relative set theory: Internal view. - Karel Hrbacek (J. Log. Anal., 2009)

Relative set theory: Some external issues. - Karel Hrbacek (J. Log. Anal., 2010)

Analysis with Ultrasmall Numbers. - Karel Hrbacek; Olivier Lessmann; Richard O'Donovan (Am. Math. Mon., 2010)

Axiom of Choice in nonstandard set theory. - Karel Hrbacek (J. Log. Anal., 2012)

Relative set theory: Strong stability. - Karel Hrbacek (J. Log. Anal., 2012)

On factoring of unlimited integers. - Karel Hrbacek (J. Log. Anal., 2020)

Infinitesimal analysis without the Axiom of Choice. - Karel Hrbacek; Mikhail G. Katz (Ann. Pure Appl. Log., 2021)

Peano and Osgood theorems via effective infinitesimals. - Karel Hrbacek; Mikhail G. Katz (J. Log. Anal., 2023)

Constructing Nonstandard Hulls and Loeb Measures in Internal Set Theories. - Karel Hrbacek; Mikhail G. Katz (Bull. Symb. Log., 2023)

Multi-level Nonstandard Analysis and the Axiom of Choice. - Karel Hrbacek (J. Log. Anal., 2024)

Errata: multi-level nonstandard analysis and the axiom of choice. - Karel Hrbacek (J. Log. Anal., 2024)