Proof of Dieudonne Criterion for Univalent Polynomials

[jem05]

hello,
i need a proof for the diedonne criterion on univalent polynomials.
i was wondering if anyone knows a book or reference where i can find it.
it says:
polyn. of degree n is univalent in the open disk iff sum(k=1 --> n) a_k sin(kt)/sint z^(k-1)
is not 0 in open unit disk, given 0 < t < pi/2
thank you

 

[jem05]

hey guys,
i worked on the problem, and i proved it, it's very cute.
anyway i did not find the original proof, but this is sufficient too.
so thank you anyway, and if someone is interested, let me know i will post the solution.