Medium designators inform the reader that an item is in nonprint format and that special equipment is needed to read or view it (29.3.6.4).

Medium designators are required for nonprint sources. The medium designator is usually placed in square brackets following the title information. One exception is journal articles. The medium designator for journal articles follows the journal title, not the title of the article.

All Internet references use [Internet], as the medium designator.

• APSnet: plant pathology online [Internet]. 2011. St Paul (MN): American Phytopathological Association . . .(website) 
• Halford NG, Curtis TY.2011. Sugars in crop plants. An Appl Biol [Internet]. . . (journal article)

Non-Internet sources include information in audiovisual and other electronic formats such as videocassette, videodisc, computer disc, motion pictures, slides, and microfiche. Use an appropriate medium designator like [CD-ROM], [DVD], [videocassette], or [micofiche].

• Gunning BES. 2010. Plant cell biology [DVD]. . .
• Anhydrous ammonia [videocassette]. . .  

Content designators are optional.