Remarks on the Spectral Properties of Tight Binding and Kronig-Penney   Models with Substitution Sequences
  We comment on some recent investigations on the electronic properties of models associated to the Thue-Morse chain and point out that their conclusions are in contradiction with rigorously proven theorems and indicate some of the sources of these misinterpretations. We briefly review and explain the current status of mathematical results in this field and discuss some conjectures and open problems. 
A. Bovier, J.-M. Ghez