NIEBEL, B. W. Methods, standars and work design#Benjamin W. Niebel, Andris Freivalds. McGraw-Hill.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNIEBEL, Benjamin W. Methods, Standars and Work Design#Benjamin W. Niebel, Andris Freivalds. McGraw-Hill.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNIEBEL, Benjamin W. Methods, Standars and Work Design#Benjamin W. Niebel, Andris Freivalds. McGraw-Hill.
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