National Productivity Board and National Productivity Association. (1986). Productivity digest (Singapore). Singapore: National Productivity Board and National Productivity Association.
Παραπομπή Chicago StyleNational Productivity Board and National Productivity Association. Productivity Digest (Singapore). Singapore: National Productivity Board and National Productivity Association, 1986.
Παραπομπή MLANational Productivity Board and National Productivity Association. Productivity Digest (Singapore). Singapore: National Productivity Board and National Productivity Association, 1986.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.