National Productivity Board and National Productivity Association. (1982). 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, 1982.
Παραπομπή MLANational Productivity Board and National Productivity Association. Productivity Digest (Singapore). Singapore: National Productivity Board and National Productivity Association, 1982.
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