cdigital.dgb.uanl.mxcdigital.dgb.uanl.mx/la/1030013948_C/1030013951_T6/1030013951… · of a...
3
cdigital.dgb.uanl.mxcdigital.dgb.uanl.mx/la/1030013948_C/1030013951_T6/1030013951… · of a mouthpiece so constructed that by an arrangement of valves the products of expiration