The Work-Factor System of Work Measurement - PMTS

 

http://wf-eng.slerahosting.com/html/wf_history.html

https://books.google.co.in/books/about/Work_factor_time_standards.html?id=GiUzAAAAMAAJ

https://books.google.co.in/books/about/Work_factor_Time_Standards.html?id=mKWZAAAAIAAJ