  It has recently been claimed by De Zela that Gleason's theorem, for
probability measures on the lattice of projection operators, can be extended to
qubits by adding assumptions related to continuity and the existence of
'eigenstates'. This amounts to a claim of the derivation of Born's rule for
Hermitian qubit observables. I point out a simple counterexample, and the flaw
in De Zela's derivation (these are equally applicable to the repetition of the
derivation given in a recent Reply). I also briefly discuss a valid extension
to qubits given by Busch.
