Information produced by most research tends to flow up through the middle of this pyramid, from the Informal and Semi-formal modes toward more formal types of publications, from Peer-reviewed through Summary. In general, material from the Informal and Semi-formal modes requires greater knowledge of the discipline to understand and use.
Undergraduate students doing research for course work will tend to explore from the "summary literature" and only infrequently using material from "informal" and "semi-formal communication" until they reach graduate study. In general, material becomes more difficult to understand and use as the reader moves toward the center of the model.
