 reserve S for satisfying_Tarski-model TarskiGeometryStruct;
 reserve a, b, c, d, e, f, o, p, q, r, s,
    v, w, u, x, y, z, a9, b9, c9, d9, x9, y9, z for POINT of S;

theorem ::: GuptaEasy:
  a <> b & between a,b,c & between a,b,d &
    b <> c & b <> d implies not between c,b,d
   proof
     assume that
H1:  a <> b and
H2:  between a,b,c and
H3:  between a,b,d and
H4:  b <> c and
H5:  b <> d and
H6:  between c,b,d;
     consider x such that
X2:  a,b,c,x are_ordered & a,b,d,x are_ordered
       by H1, H2, H3, BextendToLine;
     c,b,d,x are_ordered by H5, H6, BTransitivityOrdered, X2;
     hence contradiction by H4, BEquality, X2;
   end;
