Fitting multiple data sets with the same function

[Pepe_Le_Pew]

http://root.cern.ch/root/html/tutorials/fit/fit2dHist.C.html
http://root.cern.ch/root/html/tutorials/fit/TwoHistoFit2D.C.html
http://root.cern.ch/root/html/tutorials/fit/fitMultiGraph.C.html
[url]Fit multiple histograms with the same function
http://root.cern.ch/drupal/content/numerical-minimization