The table of period subdivision is composed of 4 columns:
RelatedLC Subject Headings: Arranged in alphabetical order [MSG or May Subd Geogstand for May Subdivide Geographically].
Period Subdivisions: Arranged in chronological order.
LC Class Numbers: Adopted from LCSH at the time of compilation. Class numbers preceded by a star (*) were supplied by the compiler, not by LC. Questionable numbers in LCSH are listed as they appear, but alternate numbers are also supplied, in brackets, by the compiler. Example: xxxxxx [*xxxxxx]