surfaces from MathCurve
Astroid : http://www.mathcurve.com/surfaces/astroidal/astroidal.shtml
Berlingot : http://www.mathcurve.com/surfaces/berlingot/berlingot.shtml
Bohemian dome : http://www.mathcurve.com/surfaces/boheme/boheme.shtml
Bonnet croisé ( Cross-cap) : http://www.mathcurve.com/surfaces/bonnetcroise/bonnetcroise.shtml
Romaine : http://www.mathcurve.com/surfaces/romaine/romaine.shtml