How do you get rid of nut grass permanently?

We have a problem with nut grass. (My mother bought dirt from a nursery and it was in the dirt) We pull it and its back in back in a week. She has used Roundup and it doesnt work. She bought a " nutgrass killer selective herbicide" by a company called Monterey this also had no effect. As you can see from pics below.
q how do you get rid of nut grass permanently, gardening, landscape
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