A note on extreme points of $C^\infty $-smooth balls in polyhedral spaces

The first author’s research was supported by Ministerio de Econom´ia y Competitividad and FEDER under project MTM2011-25377 and the Universitat Polit`ecnica de Val`encia. The second author’s research was supported by Ministerio de Econom´ia y Competitividad and FEDER under project MTM2011-22417 and the Universitat Polit`ecnica de Val`encia