16th Marcel Grossmann Meeting, 4 July, 2021 (virtual) Lecture on Cosmic Strings (R.Slagter):
3th Int Conference on Symmetry, 9-13 Aug (virtual)
Mathematical Aspects of General Relativity, 29 Aug 2021 Oberwolfach
Strings, Fields and Holograms, 11 Oct 2021, Ascona
10th Int Workshop on Astronomy and Relativistic Astrophysics, 2022, Guatamala