class RubyXL::Reference

def to_s
  if single_cell? then
    self.class.ind2ref(@row_range.begin, @col_range.begin)
  else
    self.class.ind2ref(@row_range.begin, @col_range.begin) + ':' + self.class.ind2ref(@row_range.end, @col_range.end)
  end
end