handy, try daß. 
quote:
How did you know that that was what I was reading?
The first that, or that that that is the defining, or restrictive pronoun in the sentence can probably be removed like that. Or, you can replace both thats with a which, which would require you to define that. Which that? That that. Not that that, but that that in the that that that was removed earlier and replaced by that which, which is better suited for that than that.
(ex) How did you know which book I was reading?
Here’s a helpful trick: Add a plus sign before commonly used words in Google so the search engine will be forced to add them to the search.
I did a search on Google for “+that +that” and came up with some helpful links:
http://www.rightwords.co.nz/trwmay96.html#he_said
http://www.bartleby.com/81/16383.html
http://support.microsoft.com/support/kb/articles/q167/6/55.asp
How about " I don’t know if I want to do that, but if I do do that then… whatever."
But if you do do that that you describe, what happens?
(Probably should be “that which”, but what the heck…)
curwin, I use quotes (")s with that search engine with a lot of success. I started with that 8 times, & gave up at three
“Doo doo” is the one to avoid.