  The Brezis-Browder ordering principle [Advances Math., 21 (1976), 355-364] is
used to get a proof, in the reduced axiomatic system (ZF-AC+DC), of a fixed
point result [in the complete axiomatic system (ZF)] over Cantor complete
ultrametric spaces due to Petalas and Vidalis [Proc. Amer. Math. Soc., 118
(1993), 819-821].
