I agree with jte's assessment comparing von Mises vs. Tresca.
However, when I review a Div. 2 FEA report that has von Mises stresses in it, alarm bells start to go off. This is a very good indication that your FE analyst knows NOTHING about Div. 2 analyses. I also suspect that they did not bother to provide you with membrane and membrane-plus-bending stress intensities either (or if they did, they probably did it wrong...). I am also quite sure that they didn't check to ensure that the extent to which the local membrane stress intensity exceeds 1.1*Sm was less than 1*sqrt(R*t) in the meridional direction. I've seen this so many times that I've become quite the cynic in this respect...
As far as references go, I would suggest that you take a read through Appendix 4 yourself. If you have any specific questions about it, please come back here and we will gladly answer your questions.
To answer jte's question about Div. 2 rewrite - the plan is to ballot (or at least start to ballot) in January. I wouldn't hold my breath about it hitting the street in '06 though...