Tham khảo Thợ sửa ống nước

  1. ↑ Whitney, William D., ed.. "Trade." Def, 7. The Century Dictionary: An Encyclopedic Lexicon of the English Language vol. 8. New York. The Century Co. 1895. 6,415. Print.
  2. ↑ Employment and Occupations in the Skilled Trades in Michigan, Michigan Department of Technology, Management, and Budget, Bureau of Labor Market Information and Strategic Initiatives (June 2013).
  3. ↑ Pulsifer, William H. Notes For a History of Lead, New York University Press, 1888 pp. 132, 158
  4. ↑ Middleton, The Remains of Ancient Rome, Vol. 2, A & C Black, 1892
  5. ↑ Historical production and uses of lead. ila-lead.org
  6. ↑ EW Wedlake; J Britton (1836). “Westminster Palace”. The history of the ancient palace and late Houses of Parliament at Westminster. J B Nichols and son. tr. 122. Truy cập ngày 28 tháng 6 năm 2010.