?? field f .... ??? subfield k .... a1,...,an in f, b in f .... ?? "can b be defined / expressed in terms of stuff from k tw a1,...,an ?" .... ????? .....

?? lagrange extrapolation .... ????? ....

?? some confusion here about ... ?? "eyeglasses" phenomenon ??? .... ambiguity between aj and background elt in k .... ???? ....

?? try to straighten out .... ???? .....

?? c in f(x1,...,xn) .... f(a1,...,an)= b ..... ???

???? ......