# File lib/spreadsheet/excel/writer/workbook.rb, line 487
  def write_sst workbook, writer, offset
    # Offset  Size  Contents
    #      0     4  Total number of strings in the workbook (see below)
    #      4     4  Number of following strings (nm)
    #      8  var.  List of nm Unicode strings, 16-bit string length (➜ 3.4)
    num_total = 0
    strings = worksheets(workbook).inject(Hash.new(0)) do |memo, worksheet|
      worksheet.strings.each do |k,v|
        memo[k] += v
        num_total += v
      end
      memo
    end
    _write_sst workbook, writer, offset, num_total, strings.keys
  end