It doesn ' t seem likely to me . Think about the case where the sets are identical , which should according to your hoped for result force the mapping to be volume preserving which it doesn ' t have to be . <| sep |> Hey , I think that is perhaps not a very nice thing to do . <| sep |> I can ' t find it either . We ' ve met with a terrible fate . <| sep |> considervelmenteSenhoras e senhores , eis a primeira praproparoxtona da lngua portuguesa . <| sep |> on this so fast , thanks <| sep |> shymouse , Out of all the nonmahrams to wear hijab in front of , the most emphasized is the brotherinlaw . A mahram is not someone you can ' t marry now but rather someone you can never marry . So your father , your brother , and after marriage , your father inlaw , your soninlaw , your stepson , etc . As far as your brotherinlaw , he is not your mahram because you are allowed to marry him if your husband were to pass away . Hope that helps , TheMuslimShrink