{
  gROOT->SetStyle("Plain");
  RooRealVar x("x", "x", -10, 10);
  RooRealVar y("y", "y", -10, 10);
  
  RooRealVar mux("mux", "average-x'", 0, -1, 1);
  RooRealVar sigmax("sigmax", "sigma-x'", 0.5, 0, 5);
  RooGaussian gaussx("gaussx","gaussian PDF x'", x, mux, sigmax);
  
  RooRealVar muy("muy", "average-y'", 0, -1, 1);
  RooRealVar sigmay("sigmay", "sigma-y'", 1.5, 0, 5);
  RooGaussian gaussy("gaussy","gaussian PDF y'", y, muy, sigmay);
  
  RooProdPdf gaussxy("gaussxy", "gaussxy", RooArgSet(gaussx, gaussy));

  TCanvas c;
  TH2 * h2 = dynamic_cast<TH2*>(gaussxy.createHistogram("h2", x, RooFit::Binning(100),
							RooFit::YVar(y, RooFit::Binning(100))));
  assert(h2 != 0);
  h2->Draw("surf3");
  c.SaveAs("03-pdfProduct.pdf");
}