1. W. M. Boyce, Commuting functions with no common fixed point, Abstract 67T-218, Notices Amer. Math. Soc. 14 (1967), 280.
2. Commuting functions with no common fixed point;Boyce, William M.;Trans. Amer. Math. Soc.,1969
3. J. P. Huneke, Two counterexamples to a conjecture on commuting continuous functions of the closed unit interval, Abstract 67T-231, Notices Amer. Math. Soc. 14 (1967), 284.