void multiMarkerLegend() {

   auto g1 = new TGraph();
   g1->AddPoint(0.1, 10.0);
   g1->AddPoint(0.2,  7.0);
   g1->AddPoint(0.5,  4.0);
   g1->AddPoint(1.4,  0.5);

   g1->SetMarkerStyle(20);
   g1->Draw("ALP");

   auto g2 = new TGraph();
   g2->AddPoint(0.2, 10.3);
   g2->AddPoint(0.3,  7.3);
   g2->AddPoint(0.6,  4.3);
   g2->AddPoint(1.5,  0.8);

   g2->SetMarkerStyle(24);
   g2->Draw("LP");

   TLegend *leg = new TLegend(0.5,0.7,0.7,0.85);
   leg->SetNColumns(2); // could be more columns
   leg->AddEntry(g1,"","P");
   leg->AddEntry(g2,"#pi^{#pm}","P");
   leg->Draw();
}