1. Libor Polák (1950–2020)

   • Jiří Kad’ourek
   • Ondřej Klíma

   Obituary 02 March 2021 Pages: 315 - 321

   

2. On some families of subsemigroups of a numerical semigroup

   • Fabián Arias
   • Jerson Borja

   RESEARCH ARTICLE 07 January 2021 Pages: 322 - 339

   

3. Periodic behavior in families of numerical and affine semigroups via parametric Presburger arithmetic

   • Tristram Bogart
   • John Goodrick
   • Kevin Woods

   RESEARCH ARTICLE 10 February 2021 Pages: 340 - 356

4. A generalized variety problem

   • Genevieve Churchill

   Research Article 04 February 2021 Pages: 357 - 374

5. Coverages on inverse semigroups

   • Gilles G. de Castro

   Research Article 30 September 2020 Pages: 375 - 396

6. Complete classification of finite semigroups for which the inverse monoid of local automorphisms is a \(\varDelta \)-semigroup

   • V. D. Derech

   RESEARCH ARTICLE 07 January 2021 Pages: 397 - 407

7. On sensitive sets and regionally proximal sets of group actions

   • Zhumin Ding
   • Xiaoxiao Nie
   • Jiandong Yin

   Research Article 02 March 2021 Pages: 408 - 421

8. \(\lambda \)-Semidirect products of inverse monoids are weakly Schreier extensions

   • Peter F. Faul

   Research Article Open access 31 August 2020 Pages: 422 - 436

   

9. The rank of the inverse semigroup of partial automorphisms on a finite fence

   • J. Koppitz
   • T. Musunthia

   RESEARCH ARTICLE 08 January 2021 Pages: 437 - 455

10. A simple spectral theory of polynomially bounded solutions and applications to differential equations

    • Vu Trong Luong
    • Nguyen Van Minh

    Resarch Article 02 March 2021 Pages: 456 - 476

11. Semigroup method for a deteriorating system with multiple vacations of a repairman

    • Muhtabar Muhtar
    • Abdukerim Haji
    • Abdulla Hoshur

    Research Article 09 January 2021 Pages: 477 - 494

12. A categorical approach to operator semigroups

    • Abraham C. S. Ng

    RESEARCH ARTICLE 10 February 2021 Pages: 495 - 516

    

13. DTC ultrafilters on groups

    • Jan Pachl
    • Juris Steprāns

    Research Article 06 October 2020 Pages: 517 - 527

14. Essential character amenability of semigroup algebras

    • Hamid Sadeghi Nahrekhalaji

    Research Article 04 January 2021 Pages: 528 - 542

15. A note on weak amenability of semigroup algebras 

    • Maedeh Soroushmehr

    RESEARCH ARTICLE 04 January 2021 Pages: 543 - 552

16. A construction of the free digroup

    • Guangliang Zhang
    • Yuqun Chen

    Research Article 02 March 2021 Pages: 553 - 567

17. Polynomial central set theorem near zero

    • Aninda Chakraborty
    • Sayan Goswami

    SHORT NOTE 23 February 2021 Pages: 568 - 574

18. A simple proof of a multidimensional Borg–Levinson type theorem

    • Mourad Choulli

    Short Note 19 February 2021 Pages: 575 - 582