The text of a subtitle, if any. ‘Subtitle’ means any added words which appear with the title element given in an occurrence of the <TitleElement> composite, and which amplify and explain the title element, but which are not considered to be part of the title element itself. Optional and non-repeating.

Note that subtitles should appear as they do on the title page of the book (or exceptionally, on the cover). For text that appears on the cover but not on the title page – especially text which is purely promotional – see Group P.14 and in particular, <TextType> codes for Cover line, Endorsement or Promotional headline.