%0 Journal Article %T Complexes of activity on the Sun in solar cycle 21 %A Yazev, S.A. %A Ulianova, M.M. %A Isaeva, E.S. %K solar activity, activity complexes, flares, North-South asymmetry %J Solar-Terrestrial Physics %D 2021 %N 7 %P 6 %I INFRA-M Academic Publishing LLC.