[R] What is a "good fit" Brier score and Harrel's C Index

[E Joffe]

Hi all, 

I am evaluating survival models using Brier score ("peperr") and Harrel's
C-Index ("Hmisc").
I am wondering:

1. What would be considered a "good fit" according to these scores (like the
heuristic levels we have for R square in linear regressions) ?

2. Are there any papers to cite on the matter (I couldn't find any) ?

3. Is there any paper to cite that discusses the limitation of using
traditional reporting for model fit in survival analysis as opposed to these
measures  ?

Thanks,
Erel