APA
National Standard Duncan Limited, National Standard Duncan Limited, . (1991). Annual Report, 1990-91. Calcutta: National-Standard duncon Limited.
Chicago
National Standard Duncan Limited, National Standard Duncan Limited, . 1991. Annual Report, 1990-91. Calcutta: National-Standard duncon Limited.
Harvard
National Standard Duncan Limited, National Standard Duncan Limited, . (1991). Annual Report, 1990-91. Calcutta: National-Standard duncon Limited.
MLA
National Standard Duncan Limited, National Standard Duncan Limited, . Annual Report, 1990-91. Calcutta: National-Standard duncon Limited. 1991.
