It is important to remember that yellow nutsedge is not a grass or broadleaf weed, but a sedge. There are many sedge species, but yellow nutsedge is the most problematic. Sedge control requires different herbicides and application timings than grasses and broadleaves,so understanding the biology of sedges is important.
The most recent Purdue TurfTips provides some excellent information about controlling this tough lawn weed. It is available in PDF form by clicking here.