Source:
Original audio cassette: Recorded Lectures by Professor Peter Drucker, 1974-1975; Drucker Archives; Box 102; MTG 4 Business Policy, Tape 2; OCT 74; cassette 6, side 1
Source:
Original audio cassette: Recorded Lectures by Professor Peter Drucker, 1974-1975; Drucker Archives; Box 102; MTG 4 Business Policy, Tape 2; OCT 74; cassette 6, side 2