for X being non empty set
for x being Tuple of 4,X
for a, b, c, d being object st ( a = x . 1 or a = x . 2 or a = x . 3 or a = x . 4 ) & ( b = x . 1 or b = x . 2 or b = x . 3 or b = x . 4 ) & ( c = x . 1 or c = x . 2 or c = x . 3 or c = x . 4 ) & ( d = x . 1 or d = x . 2 or d = x . 3 or d = x . 4 ) holds
<*a,b,c,d*> is Tuple of 4,X