Combinatorial R-trees as generalized Cayley graphs for fundamental   groups of one-dimensional spaces
  In their study of fundamental groups of one-dimensional path-connected compact metric spaces, Cannon and Conner have asked: Is there a tree-like object that might be considered the topological Cayley graph? We answer this question in the positive and provide a combinatorial description of such an object. 
Hanspeter Fischer and Andreas Zastrow
math.GT