public function getComment($pCellCoordinate = 'A1')
    {
        // Uppercase coordinate
        $pCellCoordinate = strtoupper($pCellCoordinate);

        if (strpos($pCellCoordinate, ':') !== false || strpos($pCellCoordinate, ',') !== false) {
            throw new PHPExcel_Exception('Cell coordinate string can not be a range of cells.');
        } elseif (strpos($pCellCoordinate, '$') !== false) {
            throw new PHPExcel_Exception('Cell coordinate string must not be absolute.');
        } elseif ($pCellCoordinate == '') {
            throw new PHPExcel_Exception('Cell coordinate can not be zero-length string.');
        } else {
            // Check if we already have a comment for this cell.
            // If not, create a new comment.
            if (isset($this->comments[$pCellCoordinate])) {
                return $this->comments[$pCellCoordinate];
            } else {
                $newComment = new PHPExcel_Comment();
                $this->comments[$pCellCoordinate] = $newComment;
                return $newComment;
            }
        }
    }