organizers were represented as paradigms, schematic representations, and diagrams as they took on more geometric shapes.

In 1969, Richard F. Barron came up with a tree diagram that was referred to as a "structured overview." The diagram introduced new vocabulary and used spatial characteristics and language written at the same level as the material being learned. In the classroom, this hierarchical organization was used by the teacher as a pre-reading strategy to show relationships among vocabulary. Its use later expanded for not only