A book by KarlFant on a clockless logic for hardware design that removes all concern for timing closures:  http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471684783.html

You can read about this online in his paper entitled "Null Convention Logic": http://www.cse.ucsc.edu/~sbrandt/papers/NCL2.pdf
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CategoryBook