Understanding Text with an Accompanying Diagram. - William C. Bulko (IEA/AIE (Vol. 2), 1988)

Understanding Natural Language with Diagrams. - Gordon S. Novak; William C. Bulko (AAAI, 1990)

Diagrams and Text as Computer Input. - Gordon S. Novak Jr.; William C. Bulko (J. Vis. Lang. Comput., 1993)