Life In 19x19

I've been enjoying going through WBaduski's tsumego collection while/between watching games there. The problem window is also handy for covering those pesky avatars. Anybody know where they (the problems) come from?

I'm not sure exactly, but I agree that it's one of the best collections on the net. The problems probably come from a variety of sources. I have seen the easier problems in many Chinese books. If you want more of the same, try out http://weiqiok.com. If you're looking for a reasonably large collection of problems at various difficulty levels in book format I recommend the Taiwanese edition of Cho Chikun's Dictionary of Life and Death. Don't be afraid of the Chinese. You don't really need to be able to read it, and if you want to it comes with a translation sheet. It has many explanatory diagrams.

"The Taiwanese edition of Cho Chikun's Dictionary of Life and Death" in two volumes. Vol 1 being available in English as "All About Life and Death 1 & 2" and Vol 2 being selected problems from Xuanxuan Qijing, Guanzipu, and Gokyo Shumyo.

The mainland China version is even cheaper and should be readily available as it was only republished in 2009.

围棋死活辞典(上卷) ISBN 9787538160864
围棋死活辞典(下卷) ISBN 9787538160857

Thanks for the response. I have several books of tsumego here at home, enough to keep me busy for a long-long-time. Just curious were the collection were taken from. I really prefer books when it come to working through problems. That I found myself going through so many of WBaduks tsumego was the first indicator that this is a collection of quality.