Closure.

Since their inception [186] in 1990, a substantial volume of literature on Pythagorean—hodograph curves has accumulated — the bibliography includes over 80 papers concerned with elucidating the basic theory of PH curves, their extensions and generalizations, algorithms for their construction and analysis, and their applications in computer—aided design and manufacturing, robotics, motion control, graphics and animation, and related fields. Nevertheless, many problems merit further study, and research on PH curves remains very active. A forthcoming special issue of Computer Aided Geometric Design is devoted to the theme "Pythagorean—hodograph curves and related topics." [ABSTRACT FROM AUTHOR]