[Haskell-cafe] Combinations

Hi, I need a functions which takes as argument a list of lists like this one: [[1,2],[3],[4]] and gives me a list of list with all the possible combinations like this one: [[1,3,4],[2,3,4]] In this case there are only 2 combinations but if there was more than one element in the other lists the results were much more. I'm a little stuck in this simple problem. First i was thinking in cartesian product but then i realized that i may not be what i really need. Any tip? Many thx, Nuno Santos