there are many books and there are many scholarly articles, but these days information on line is what works the best.
Personally I find that there have been, over the years, some sites from which I got much help and information.
One is certainly
http://old.blades.free.fr, admittedly the navigation isn't very intuitive but once you get to explore this you will get a lot of information, please explore (as I said the exploration isn't as intuitive as it may be), there is a LOT there not only on krises but also other edged weapons from the area and way beyond