Here are two further references of proofs of the fixed point theorem that rely on evaluating determinants: MR0117523 Dunford, Nelson ; Schwartz, Jacob T. Linear Operators. I. General Theory. With the assistance of W. G. Bade and R. G. Bartle. Pure and Applied Mathematics, Vol. 7 Interscience Publishers, Inc., New York; Interscience Publishers, Ltd., London 1958 xiv+858 pp. The proof is on page 467. MR0610487 Kannai, Yakar . An elementary proof of the no-retraction theorem. Amer. Math. Monthly 88 (1981), no. 4, 264--268.