<< MathWorldCurves

Thanks. I guess it must be part of the list of server-side packages, like "UtilitiesLiveGraphics3D" in e.g. Slinky.nb. Best would be to write directly to Eric Weisstein, the maintainer of the site. If you do so and he replies, be sure to add an answer here! –  István Zachar Mar 8 at 8:47