They seek readmission to the United States. Some have come to the United States. In seeking readmission they are denied the usual courtesy and visas that tire granted to American citizens. because it is said that the presumption of expatriation deprives them of all right that a citizen should have. Then. when they return to the United States. the question arises. even when they come in good faith. as to whether they are American citizens and as to the effect of presumption of expatriation. Some of the courts have held that they are not citizens. others have held that they are citizens. or. at any rate. the former have held that the burden of prQof is upon them. and that it requires very certain and definite proof in order to establish the fact that they are citizens of the United States.