multiple liability immunization: Match PV, discounted at IRR??

I was reading CFAI and schweser, no where showed any clue about the fact that PV must be discounted at IRR.

anyone can point me to the right source?

Is it 2010 q6 you are reffereing to

refer to my answer here :

Believe they say YTM in text…that is the IRR for a bond.

from CFAi

_ The performance of a multiple liability immunized plan can be monitored most easily by comparing the current market value of the assets with the present value of the remaining liabilities. The current internal rate of return on the immunized portfolio should be used to discount the remaining liabilities. _

(Institute 45)

Institute, CFA. Level III 2013 Volume 4 Fixed Income and Equity Portfolio Management. John Wiley & Sons P&T, 6/18/2012. .

^^ exactly