A work on two or more otherwise independent topics is assigned one or more subject headings depending on the number of topics involved, the nature of their treatment in the work, and the availability of pre-coordinated headings.

26.61 Works on two or three topics treated separately

26.62 Works on four or more topics treated separately

26.63 Works on two or more topics treated in relation to each other

See also:

26.0 Number of headings