ACKNOWLEDGMENTS
We thank D. J. Ward for lengthy discussions that enhanced the quality of this paper and helping to improve the English, and M. V. Nazarkin for help in preparing the article. Editors J. Harris, C. Underwood, A. López-Arbarello and reviewers made constructive suggestions for improvement of the manuscript. The study was funded by RFBR and National Research Foundation of Korea: research project no. 19-54-51001 under the framework of international cooperation program managed by the National Research Foundation of Korea (2019K2A9A1A0609922511), as well as State task of the IGG UB RAS no. AAAA-A18-118052590025-8.