Selk, J. (2018). Executive toughness: The mental-training program to increase your leadership performance (Updated edition.). McGraw-Hill Education.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रSelk, Jason. Executive Toughness: The Mental-training Program to Increase Your Leadership Performance. Updated edition. New York: McGraw-Hill Education, 2018.
एमएलए (8वां संस्करण) प्रशस्ति पत्रSelk, Jason. Executive Toughness: The Mental-training Program to Increase Your Leadership Performance. Updated edition. McGraw-Hill Education, 2018.
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