Nevin Lianwen Zhang Runping Qi David Poole Incremental computation of the value of perfect information in stepwise-decomposable influence diagrams. 400-410 1993 conf/uai/1993 UAI http://rome.exp.sis.pitt.edu/UAI/Abstract.asp?articleID=605&proceedingID=9 db/conf/uai/uai1993.html#ZhangQP93