Fast Boundary Detection: A Generalization and a New Algorithm. - Werner Frei; Chung-Ching Chen (IEEE Trans. Computers, 1977)

Rate-Distortion Coding Simulation for Color Images. - Werner Frei; Brent Baxter (IEEE Trans. Commun., 1977)

Relaxation labeling using continuous label sets. - James S. Duncan; Werner Frei (Pattern Recognit. Lett., 1989)