**PREPRINTS**

**1. Ab5-star Abelian groups
(1987).**

**2. Extending Abelian groups
(1999).**

**3. Dual Zassenhaus Lemma
(2003).**

**3. Schreier Lattices
(2005).**

**4. Determination of
torsion-free Abelian groups by their direct powers (2006).**

**5. Intersections of principal right ideals in
regular rings are principal: a direct proof (2008).**

**6. Abelian groups with
dual endomorphism ring (2009).**

**7. Abelian groups with
unit-regular endomorphism ring (2009).**

**8. Extensions by factor sets for some lattices
(2010).**

**9. Sections and retractions in the category Grp
(2010).**

**10. On unit-regular rings
(2010).**

**11. Abelian groups with reduced endomorphism ring
(2014).**

**12. Additive groups of rings with identity
(2014).**

**13. Regular Abelian groups and elements
(2016, revised 2018).**

**14. Uniquely fine 2 × 2 integral matrices
(2016).**

**15. Similarity and class numbers. Clean 2x2 integral matrices
(2017).**

**16. Exceptional units in matrix rings
(2018).**

**17. Exchange 2 x 2 matrices over principal ideal domains: a characterization
(2019).**

**18. Examples of equivalent matrices that are not similar
(2021).**

**19. Similarity for zero-square matrices
(2021).**

**20. A nil-clean matrix example improved by computer
(2021).**

**21. A 3 × 3 nilpotent matris of index 3 which has unit
Stable range one
(2021).**

**22. On products of stable range one elements
(2022).**

**23. A zero determinant 2 × 2 matrix which has not
stable range one
(2023).**

**24. On the recognition of upper triangular matrix rings
(2023).**

**25. Unipotent-regular matrices and rings
(2023).**

**26. An idempotent not conjugate with its complementary idempotent
(2024).**

**27. Negative nil-clean rings
(2024).**