Local magnetic properties of periodic nonuniform spin-1/2 XX chains
  Using the Jordan-Wigner fermionization, Green function approach and continued fractions we examine rigorously the local magnetizations and the local static susceptibilities of the spin-1/2 XX chain in a transverse field with regularly varying exchange interactions. We discuss our findings from a viewpoint of the strong-coupling approach. 
Oleg Derzhko, Johannes Richter, and Oles' Zaburannyi