There are four books I can think of that specifically deal with the 509.
WE JUMPED TO FIGHT by Edson Raff--the commander of the 509 in N. Africa and Italy.(Long out of print and a real collectors item)
HOME WAS NEVER LIKE THIS (the Yardley Diaries) by Charles Trumbo recently published diary format.
STAND IN THE DOOR by Charles H. Doyle.Comprehensive history of the 509.
BAIL OUT OVER NORTH AFRICA by William Yarborough
You should find several hits on the 509 on a GOOGLE search.If memory serves part of the 509 is still in operation as a seperate Pathfinder detachment and last I heard they were on permenant station in Italy.
I just looked at the calander and it appears that the anniversary of his capture will be next week--29FEB--an interesting date as it only comes around once every four years!