Gemara in Menochos 43b
???? ??? ??? ???? ???? ???? ????? ?? ??? ???? ?????? ?? ???? ??? ??? ???? ???? ???? ??? ??? ???? ???? ????? ???? ??? ??? ?? ???? ?? ??? ????? ??? ??? ?? ???? ?? ??? ????? ????? ??? ????? ???? ??? ????? ????? ??? ???? ?? ???? ?? ??? ?? ???? ?? ??? ??? ????
Rashi says ???? ????? ??
???. ??? ????? ???? ?????
?????
Mashma when someone is wearing neither he is oiver
Rambam in tzitzis 2:9
??? ???? ?? ????? ???? ??? ???? ????? ??? ???? ???? ??? ????? ???? ??? ?????? ???? ????? ??? ???? ??? ??? ??? ???? ???? ??????:
it is mashma we are talking about when both are available.