This problem is from Guanzi Pu – possibly my favourite of the classic problem collections thanks to its varied and relatively difficult problems.
While a (most likely illegal) pdf version of the book been posted around on Western go websites, its solutions often seem to be wrong. I would instead recommend interested players to invest in a six-volume physical copy, which can for example be bought from Hebsacker Verlag.
Black to play.
All times are in Helsinki time (eet with summer time).
Pixel Go Tournament on October 31, 12:00–15:00! Tournament details and registration are here.
New pairing for the online league made every 1st and 3rd Saturday of the month.
Public lectures on Twitch every 2nd and 4th Saturday of the month at 1 pm.
Jeff and Mikko stream on Twitch on Fridays at 6 pm.