The milestones items have been classified into hierarchical categories as an aid to researchers
wishing to examine this material by thematic groups.
The categories of
Content (Section
11.1) relate to the substance or subject matter of the milestone or innovation-
what is was
about. Some of the main category headings are Astronomy, Commerce, Education,
and Social science.
The categories of
Form (Section
11.2) relate to the graphic or technological details of the
milestone item- what it
consisted of.
Some of the main categories used here are graphic types or elements: Chart, Curve, Diagram, etc.
The entries in the listing are the item keys, in the form
yearName,
from the chronlogical listing.
In this version of the cross-reference, a given item can appear at several levels in the
hierarchy, representing broader or narrower categories.