This special issue of the Journal of Mathematical Sciences (Volume 266 Number 3, 2022) has been established in honour of professor Stefan Samko, Doctor of Sciences, on the occasion of his 80-th birthday. This thematic collection was preceded by the activities within the framework of the OTHA international conference in 2021 which was dedicated to the 80th anniversary of S.Samko.
Guest Editors: Alexandre Almeida (Portugal), Zalina Kusrayeva (Russia) and Humberto Rafeiro (UAE).

This special issue ((Volume 266 Number 1, 2022) of the Journal of Mathematical Sciences (Series A) has been established in honour of Professor Nikolay Karapetyants (1942-2005), Doctor of Sciences, on the occasion of 80-th anniversary from the date of his birthday. This thematic collection was preceded by the activities within the framework of the OTHA international conference in 2022 which was dedicated to Professor N.Karapetiants. This issue is the first in a series of direct submissions (Series A) launched in 2022.

This thematic collection of contributed articles has been established in honour of professor Stefan Samko, at the occasion of his 80-th birthday. The contributions provided have been written by colleagues, on the basis of an invitation through the guest editors. Each of those papers sheds some light on at least one of the many research directions which have played a role in the S.Samko scientific career. This thematic collection was preceded by the activities within the framework of the OTHA international conference in 2021 which was dedicated to the 80th anniversary of S.Samko.
Editors: Alexey Karapetyants, Vladislav Kravchenko, and Elijah Liflyand.

This is the first in the two-volume series originating from the 2020 activities within the international scientific conference "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis" (OTHA), Southern Federal University in Rostov-on-Don, Russia.
Editors: Karapetyants A., Kravchenko V.V., Liflyand E., Malonek H.R.

This is the second in the two-volume series originating from the 2020 activities within the international scientific conference "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis" (OTHA), Southern Federal University, Rostov-on-Don, Russia.
Editors: Karapetyants A., Pavlov I. V., Shiryaev A. N.

This proceedings volume gathers selected, peer-reviewed papers from the "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis IX" (OTHA 2019) conference, which was held in Rostov-on-Don, Russia, in April 2019.
Editors: Alexey Karapetyants, Vladislav Kravchenko, Elijah Liflyand

This proceedings volume gathers selected, peer-reviewed papers from the "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis VIII" (OTHA 2018) conference, which was held in Rostov-on-Don, Russia, in April 2018. Prepared in the framework of ISAAC-Springer agreement.
Editors: Alexey Karapetyants, Vladislav Kravchenko, Elijah Liflyand

These issues gather selected papers from the "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis VII" (OTHA 2017) conference, which was held in Rostov-on-Don, Russia, in April 2017.

The issue gathers selected papers from the "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis VI" (OTHA 2016) conference, which was held in Rostov-on-Don, Russia, in April 2016.

The issue gathers selected papers from the "Modern Methods, Problems and Applications of Operator Theory and Harmonic Analysis V" (OTHA 2015) conference, which was held in Rostov-on-Don, Russia, in April 2015.