Making Database Schema Hierarchical for Visual Access to Databases. - Ping-Kuen Chen; Gwo-Dong Chen (Knowl. Inf. Syst., 1999)

HVQS: The Hierarchical Visual Query System for Databases. - Ping-Kuen Chen; Gwo-Dong Chen; Baw-Jhiune Liu (J. Vis. Lang. Comput., 2000)