19th edition, V. D. Mazurov (ed.), E. I. Khukhro (ed.), Novosibirsk, 2018; https://kourovka-notebook.org/
This collection of open problems in group theory has been published every three–four years at Novosibirsk Institute of Mathematics since 1965. Problems have been proposed by hundreds of mathematicians from all over the world, the difficulty of problems ranges from PhD level to well-known problems that remain open for decades.
The current 19th edition contains 111 new problems and a number of comments on problems from the previous issues. The section “Archive of Solved Problems” includes all the solved problems from the previous issues that have already been commented on in previous issues (but new solutions are found among unsolved problems in the corresponding sections!).
More than fifty years “Kourovka Notebook” serves as a unique means of communication for researchers in Group Theory and nearby fields of mathematics. Probably the most striking illustration of its success is the fact that more than three-quarters of the problems from the 1st edition of 1965 have now been solved.