Bell Telephone Laboratories, Incorporated (1979). "Unix Seventh Edition Manual". Murray Hill, NJ: Alcatel-Lucent Bell Labs. Archived from the original on 2008-10-19. Retrieved 2011-04-23. Online archive of the manual pages included with the Seventh Edition Unix distribution tapes.
Bell Telephone Laboratories, Incorporated (1979). "Unix Seventh Edition Manual". Murray Hill, NJ: Alcatel-Lucent Bell Labs. Archived from the original on 2008-10-19. Retrieved 2011-04-23. Online archive of the manual pages included with the Seventh Edition Unix distribution tapes.
As specified from several NetCDF conventions, e.g.: