Dear list members

I wonder if anyone could direct me to studies on the thirteenth-century
saint Ambrose of Sansedoni (sometimes of Sienna)? I have been hunting
around and have come up with very little thus far. I am particularly
interested in looking at his posthumous cult, especially the 
relationship between the two _vitae_ which have been printed in the Acta
Sanctorum (Mar.III). 

Many thanks in advance,