How i can show the tooltip with same point in same position ?

[Xuân Hiển Ngô]

  function drawMouseoverVisualization() {
    var data = new google.visualization.DataTable();
    data.addColumn('string', 'Year');
    data.addColumn('number', 'Score');
    data.addRows([
      ['2005',3.6],
      ['2005',3.6],
      ['2007',3.8],
    ]);
Let imagine that i have 3 lines with 2 lines same value at 2005 how i can show the tooltip with full data of 2 year ?