Online defensive tactics training problems? I've been doing the tactics problems at jrobichess.com and shredderchess.com pretty regularly, and recently added chesstempo.com. I find I'm much better at attacking tactics than defensive tactics: that is, I can solve "Find mate in X"-type problems at a much higher level than "Avoid mate"-type problems, even when the calculations are basically the same. I know how to deploy various attacking ideas, but I haven't learned to see them coming and defend against them. What are some resources I could use to improve this side of my tactical play? Is there a site like the above that stresses defensive tactics, or where you can select specifically defensive problems?
I enjoyed Andy Soltis' The Art of Defense in Chess.  It was all about finding hidden resources.

Remarkably, this book is available electronically for no cost, and legally I assume.  Here are a few links.

http://torrentz.eu/solt/Soltis%2C%20Andrew%20-%20The%20Art%20of%20Defense%20in%20Chess.pdf-3692550

http://ebookee.org/The-Art-of-Defense-in-Chess-by-Andrew-Soltis-1975-_1168031.html

Paper book:
http://www.amazon.com/The-Defense-Chess-Andrew-Soltis/dp/0679141081