Polaron model of pseudogap state in quasi-one-dimentional systems
  A brief overview of the basic concepts and problems of the physics of quasi-one-dimensional compounds is done. Consistent theoretical description of the so-called pseudogap state remains the main problem. A simplified model of the pseudogap state, based on the picture of small polarons formation in the framework of cluster perturbation theory is considered. 
Yu.S. Orlov and V.A. Dudnikov
cond-mat.str-el