Pion--Pion Scattering Experiments at Low Energy
  This work reviews the available experimental information on the pi-pi scattering lengths, especially the recent near-threshold pi N -> pi pi N data from several laboratories and the related application of the Chew-Low-Goebel (CLG) technique well below 1 GeV/c momentum. At this time uncertainties stemming from non-pion-exchange backgrounds in near-threshold CLG studies appear to preclude a determination of the pi$-pi scattering lengths with the desired accuracy of 10% or better. 
D. Pocanic (Univ. of Virginia)