Invested Capital

Looking for some clarification regarding invested capital in EVA analysis. I have seen some different definitions of invested capital e.g. Book Value of Assets, Book Vlaue of Long Term Debt + Book Value of Shareholders Equity. Some of the definitions are not always consistent. Does anybody have a foolproof method for deriving invested capital? Mike

i just did a qestion on this (granted it was schweser) and they seemed to use BV of LTD + BV of Equity…believe thats the one that gets used the most?