Please suggest what can I do with these sweet limes?

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Hello all, I bought over a dozen Sweet limes of teh green skinned variety. The grocer assured me that they were all ripe and sweet and even offered me a slice of teh fruit, which was nice and sweet. But the ones that I brought hope home turned out to be still a little raw and more sour than sweet. Now he refuses to take them back, and seriously, I cannot just force the limes on the poor guy. But now I am left with 12 of these fruits and really do not want to just throw them 'coz they cost me good money. Can anyone tell me some ways to use this, perhaps make some kind of preservative or something similar??