100 Challenging Go Problems for 100 Days of StudyBy: The Nihon Ki-in Publisher: Yutopian, 1995 Buy online: https://www.yutopian.com/yutop/cat?product=PAY05&category=PAY
Yutopian book. Consists of difficult (mainly) problems from Kido magazine. All areas of the game are covered.
David Carlton's review (with Tom Roseís comments)
to be added