The hydrogen Lamb shift and the proton radius
  The Lamb shift measurement and theory are now both a dynamically developing field and we give a review of the current data. Critical comparison of theory and experiment can be done using a value of the proton charge radius and we pay attention to several results of its determination. 
Savely G. Karshenboim (D. I. Mendeleev Institute for Metrology, St.   Petersburg and Max-Planck-Institut fuer Quantenoptik, ...