consider A being non empty set , b1, b2, b3 being BinOp of A, e being Element of A;
take QuasiNetStr(# A,b1,b2,b3,e #) ; :: thesis: not QuasiNetStr(# A,b1,b2,b3,e #) is empty
thus not the carrier of QuasiNetStr(# A,b1,b2,b3,e #) is empty ; :: according to STRUCT_0:def 1 :: thesis: verum