On a coefficient problem for bi-univalent functions

The function f(z) will be called bi-univalent if both f(z) and f-'(z) are univalent in I zI < 1; f(z) will be said to belong to oiff (i) f(z) CS and (ii) there exists a function g(z) ES such that f(g(z)) =g(f(z)) = z in some neighborhood of the origin. Z. Nehari remarked1 that if 4(Z) =4lz+02z2+ ... and i,V(z) lZ +V/2Z2 + * *, with 41, =41, are two functions mapping the open unit circle onto a schlicht domain containing the open unit circle, then the function