Field 321 is used for former frequencies. When this field is given, a designation must be also included in all fields (310 and 321). As with other notes, dates are generally given but numbers may also be used. When the exact date range is unknown, give what is known in angle brackets. Do not give field 321 without field 310. Do not include a designation when only the current frequency is given in field 310 since it is assumed that this is the frequency for all issues beginning with the first. If the serial has changed its frequency many times, you may give only the current frequency and use a "Frequency varies" note in field 321. For more information, see CEG 310/321. Example:

See also:

13.3. Frequency notes (fields 310/321)