This question is really no more than a reference request, but here's some background for those who are interested:
In Peter Muller's paper "A Weil-Bound Free Proof of Schur's Conjecture" (available for viewing here), where he proves the statement that
A polynomial $P$ that is bijective over infinitely many finite fields is a composition of Dickson polynomials and polynomials of the form $ax^m+b$ for some $a,b,m$,
the conjecture of which is due to Issai Schur, the first theorem proven is as follows:
Let $K$ be a number field, with $\mathcal{O}_K$ its ring of integers. We say that a polynomial $f\in \mathcal{O}_K[x]$ is exceptional if the following holds. For infinitely many nonzero prime ideals $\mathfrak{p}$ of $\mathcal{O}_K$, $f$ as a function on $\mathcal{O}_K/\mathfrak{p}$ permutes the elements of this field.
THEOREM 1. Let $f\in \mathcal{O}_K[x]$ be an exceptional polynomial of degree $n\geq 2$. Let $t$ be a transcendental over $K$, and let $x_i (1\leq i\leq n)$ be the roots of $f(X) - t$ in some algebraic closure of $K(t)$. Then
$$\sum_{i=1}^n \zeta^i x_i=0$$
for $\zeta$ an $n$-th root of unity and a suitable numbering of the $x_i$.
He mentions the following:
Schur had this assertion on page 128 in his paper [8] from 1923 for $K=\mathbb{Q}$. Of course there was no Weil bound (or sufficiently strong substitute) available at that time. Schur used a quite complicated series of arguments, involving the Lagrange inversion formula for power series and computations with multinomial coefficients. Further, Schur's method seems to work only for $K=\mathbb{Q}$.
I've been trying to find the paper [8] mentioned here, as I want to see Schur's argument. The citation of this paper is
I. Schur, Über den Zusammenhang zwischen einem Problem der Zahlentheorie und einem Satz über algebraische Funktionen, S.-B. Preuss. Akad. Wiss. Berlin (1923), 123-134.
Unfortunately for me, I do not know German, so I cannot properly find or navigate any archives that might contain this journal. I can find a couple websites that have some years of this journal, but none contain records from 1923.
Where might I find this paper?