function getYahooFinanceData(stockSymbol, startDate, endDate) {
  stockSymbol = stockSymbol || 'GOOG';

  var start = new Date(startDate),
    end = new Date(endDate),
    data = [];

  var url =
    'http://real-chart.finance.yahoo.com/table.csv?s=' +
    stockSymbol +
    '&a=' +
    start.getMonth() +
    '&b=' +
    start.getDate() +
    '&c=' +
    start.getFullYear() +
    '&d=' +
    end.getMonth() +
    '&e=' +
    end.getDate() +
    '&f=' +
    end.getFullYear() +
    '&g=d&ignore=.csv';

  var response = UrlFetchApp.fetch(url, { muteHttpExceptions: true });

  if (response.getResponseCode()) {
    var textFile = response.getContentText();

    // If the URL is incorrect, Yahoo will return a 404 html page and not a CSV
    if (textFile.indexOf('') == -1) {
      var csv = Utilities.parseCsv(textFile);
      for (var i = csv.length - 1; i > 1; i--) {
        data.push(csv[i]);
      }
    }
  }

  return data;
}